In BP we have suffered enormously from this problem when re-launching websites within our Interwoven set-up.  A recent case -study / guide was written internally to advise our web community on this issue.  I have summarised the key points below however I am happy to share the case study if anyone would like to read it.
 

10 considerations when upgrading your site to avoid traffic loss and SEO exclusion

1. Measure your web performance including website traffic and SEO ranking to be able to accurately understand the impact of site changes in the Search Engines.
2. Verify your website with the Search Engine to allow for greater control during periods of change.
3. Ensure that a ‘page not found’ error page template is available within both the new and old site.
4. Contact link partners inside and outside of the organisation.
5. Update Google, Yahoo and MSN with new sitemaps for faster indexing.
6. Ensure ‘Permanent’ redirects are placed on the old site to inform the search engines of the whereabouts of new content.
7. Inform 'Internal Search' of any site closures. (Useful for larger corporates)
8. Ensure legacy URL’s are re-pointed.
9. Consider Paid Search (PPC) as a means to ‘top up’ your Search presence until your natural listings improve.
10. Continually monitor, measure and tidy-up your links to regain your ranking.

In summary the key has been the permanent redirects as per the other threads today however don't overlook the community and in-bound links who will undoubtedly be linking to OLD urls.  Inform as many as possible as soon as possible of the changes.  Working with Google to force an early crawl also will help.

Regards  Matt

On 09:52:38 11 August 2008 Ashley wrote:

Sometime around the end of September, or early October, E-consultancy.com (this site) is due to relaunch.

It'll be broadly similar in content and structure to the current site but have a load of new stuff, a new design, a new brand identity etc.

The site will be hosted in the United States (currently in the UK) and will be at "econsultancy.com" rather than the current www.e-consultancy.com i.e. no 'www' sub-domain and dropping the '-'.

Effectively, then, in Google's eyes we could appear a new site, with a new domain, on a new IP range (in a different country).

Which, given our good natural search rankings at the moment, could well be tantamount to SEO suicide. 

We're keen to track, and publish, the results of what we do so that others can learn - possibly from our mistakes! I'm sure it'll be much more interesting if it goes wrong than if it goes right. Maybe if it all goes horribly wrong then at least we'll get a load of links to the 'new site' from the resulting PR ;)

The one thing we're concentrating on doing as well as possible is making sure that the correct redirects are in place, at a page level, so that PageRank should transfer from old to new. But we still might lose our overall domain credibility / authority. And, if so, we're not sure for how long.

What experience have others had of this? Any things which have turned out to be particularly important (or unimportant)? What's worked and what hasn't?

Regards

Ashley Friedlein
CEO
E-consultancy.com

See this post at the Google Webmaster Central Blog, "Best practices when moving your site".http://googlewebmastercentral.blogspot.com/2008/04/best-practices-when-moving-your-site.html

Note their refences to use of Google's webmaster tools. In the past I've found that these tools are a real time saver when making major changes to a site.

You say...

"I believe storing the databases outside Europe is different to transferring it outside for processing - and I think users and members would maintain that too."

I'm not quite convinced about the second part. I would say that, as far as web sites are concerned, most users are not concerned at all where their personal info resides. Those who are concerned are aware that many UK sites are hosted abroad -- I have never come across anyone who hasn't used a site because he/she doesn't want their info to physically exist outside the UK.

As far as the first part of your statement is concerned, what you believe is... what you believe. What are the specific legal issues at hand?

Thanks for the quote on your blog ;) I was about to reply but then I had a look at your privacy policy and was a bit concerned about the following:

"When you give us personal data, those data may be sent electronically to servers anywhere in the world and may be used, stored and processed anywhere in the world, including countries outside the European Economic Area (EEA). (Bear in mind that many countries outside the EEA do not adequately protect your rights as a data subject.)"

Also, there is no mention where your data is stored.

Once you've re-directed all of the old pages to the new pages it pays to take time to add the old pages to your disallowed list in your robots.txt file and then going into google's webmaster tools and removing them from its index.  around two months after the site move.

Although this will see a drop in natural visitors at first as your old pages are dropped from the index, you'll find that the new pages get picked up far more quickly for your keywords although it doesn't seem to work very well with Yahoo.

Are you sure you want to host it in the UK? You're better off having a UK server for optimising in Google UK results if that's where your market is.

Also - you're going to need to have a 301 redirect mapping plan to make sure everything is moved across correctly to the new domain.

Risky -yes - is it worth it for you?