Most search engines don't care particularly much about duplicate content. From research, it appears that Google considers parked domains as duplicate content and penalizes these sites in the rankings. Althougt most domains (xyz.com / 123.com) do appear to get 'merged' after awhile, for sites that want to park multiple domains, one of two things should be done.

1) Creates two separate accounts: the main domain account and an account that supports only the 'parked domains'. On the parked account, use a 301 redirect to the main site. Supposedly, this tells the Google that the URL is permanently moved and passes the duplicate content test.

2) If you are utlizing cPanel, add an 'Add-on Domain' of the domain you would like to park. Then, setup a redirect to the index of the main site. This creates as similar 301 permanent redirect that passes muster as non-duplicat content.

In both cases, one should utilize a Header checker to gauge what the Spider sees. Keep in mind that this technique has been known for sometime and comes up regularly.

From what I've gathered, the Jagger update addressed links, age/history of a site and how a site is built.

First links. The bottom line is that the way incoming links are now be counted or weighted has changed. This is Google's attempt to fight pop sites or unnatural link building/buying campaigns.

Next History. How long a domain and its individual pages have been around factors in more so than at any time before. Historical data takes on new meaning. Look for MSN/Yahoo to move in this direction in the future.

Last Structure. Standards compliance and architecture takes on new meaning now. This has increasingly been the case.

Here's some links to some interesting articles on the subject:

http://www.pandia.com/sew/112-on-the-google-jagger-algo-update-part-1.html

http://www.searchenginejournal.com/index.php?p=2563

http://www.webpronews.com/topnews/topnews/wpn-60-20051110GooglesJaggerUpdateDustBeginstoSettle.html

http://www.searchenginelowdown.com/2005/11/jagger-or-jger-googles-update.html

http://evolt.org/node/60553

SEOs refer to it as 'the sandbox' - it's the phenomenon that new sites go through in getting indexed properly on Google. Although these recommnedations may not speed the process along by much, they help when the spider comes..

1) Publish Some Pages - Any Pages - The whole theory of waiting for the site to be 'perfecto' needs to be tweaked. Publish some pages that - betas if you will - so something is online. You can continue to tweak/polish.

2) Link To The New Site from Existing Google Site - There are theories that the aging delay is to combat 'pop sites' that utilize link networks. Borrowing slightly from this concept, link to the new site from an existing one already indexed in Google. Preferrably a site in the same keyword sphere.

3) Don't try those aged-content tricks - There's a school of thought that combines an aged domain content, a subdomain and a redirect to fool the spider and jimmy the rankings. The jury's is out on this - stick with the basics.

Overall, there is ongoing debate in the SEO community if the delay even actually exists, or is just a phenomenon of sort algorithmic coincidence. People make points for and against. What is known, however, is that Google constantly is changing their algorithm. Some of the updates include some major changes. I believe there were three of these this year, the last one dubbed 'Jagger' happened in early October.

I'm currently reading a new book titled 'Ambient Findability' (O'Reilly). It is a book on the deeper aspects of human wayfinding and written by Stephen Moorse. Its quite an interesting read - although a little long on high level views and abstraction. But he brings up some profound concepts to think about in relation to the future of finding information in a digital world.

The basic premise of the book is that digital data will only increase and with it, findability of what you are looking for (at the right time) will become increasingly difficult. This is in part due to the very nature of the 'technology' that allows us to communicate - language.

Since language can be quite subjective (the same words have multiple meanings; as contexts change, meanings sometimes change with them), findability will always be challenging.

All of this got me to thinking as much about the basic optimization practices on page, as well as them from an architectural standpoint. What if a CMS used this sort of concept with url structures? It could be the basis of better search on site.

What if content development centered around spheres of keywords, and as Morville pointed out, that mutli-disciplinary teams worked in tandem to generate textual-based mappings of the products, the orgnanization, ect?

Morville did get a bit out there. While it certainly wasn't a 'how-to' book, it got you thinking. Especially how some of the higher-level stuff like RDF, ontologies and stuff like that.

Update - 12/06/05
Well, what's very interesting is my point about 'keyword webs' and 'spheres of keywords' is actually known at 'latent semantic indexing (LSI)' What LSI basically does is consider a site's copy in relation to other site's that have used similar phases, keywords, etc. Basically it's a more downline approach that considers other resources and how your content relates to that 'standard'. Its latent.

A very interesting thing about my thoughts on this is that I've pondered this well before I even heard of a local interactive company that is promoting the concept. It's being promoted by a bigtime thought-leader in the SEO field. There language has given my concept a bit more structure.

A quick search on the topic found this excellent article:
http://research.nitle.org/lsi/lsa_definition.htm

When you really think about the following tips, it starts to run deep. Like Zen deep. Some of these are basic; others more involved.
Here's what they boiled down to - my summary:

1) Beware of New Domains - New domains are in Google's sandbox for 9-12 months. This is not BS. It's the perfect time to build content and fine tune content workflows. Realize this fact for new ventures. Yahoo and MSN are much more friendly these days.

2) Feel Your Audience - This helps you write content and copy geared towards them. What they're looking for. Finding you becomes easier.

3) Pay Attention To Info Architecture - How you design and adapt the information and navigational system on your site matters. Try to integrate what people are searching for into your navigational elements/architecture.

4) Pay Attention to Interaction Design - Think of this as a combination of #3 and technical writing. Design your interaction elements (link names, alt tags, link text) with your audience and terms in mind.

5) Make Sure Your Site is Friendly to Spiders - That razzle-dazzle database-driven content probably sucks as far as spidering goes. Human readable URLs, clean directory structures, strong inter-linking are important. Make it easy on the bots...

6) Use Your Title Tags with GREAT Care - These are weighed heavily. Use them with care and creativity. It's not just about jamming them with every keyword and hoping for the best. Description phrases are also important.

7) Publish Good Content That Promotes Links - Everybody has something worthwhile to say. Publish content that offers insight, infor or interest. People will link to you because of it. The more links the better.

8) Don't Be Obsessed with Number 1 - Anywhere on the first page is good. (I actually prefer being 3 or 4). This is where #6 comes in.

Over the past couple of years, I have purposefully neglected to build site traffic. Frankly, if I had set out to build traffic, I probably would have relied on some sort of affiliate program, a link farm of some sort (my first thought I mini-blinds).

Lately, I have noticed a substantial increase in traffic due to this web-log. People come in from all over regarding my posts about Southwest Airlines. What does this have to do with SEO?

The point is this: All of my postings revolve around the concept of integrated marcom. In one way or another, they seek to point out examples, thoughts or ideas that organizations are using to market and communicate more effectively. So while my topics are broad, they all seek a common purpose.

In doing so, I realized that this content also becomes 'search hooks' that attract site traffic and improve rankings.

The upside to all this is stronger brand credibility, increased eyeballs and more sales opportunities. Plus, it's good content that search engines like to index and other people like to link to.

There's been a lot written recently about web logs and what they mean to business. That's my take on it.