I have had various issues with a domain name of my site used for offline marketing making it onto Google somehow and ( to the best of my knowledge ) causing ranking problems with my search engine optimised domain ie www.keyword1-keyword2.co.nz vs www.brandname.com .
I think I may have solved at least some issues with a 301 redirect on the branding domain ... however, how does this 301 effect search engines other than Google? Is it a standard redirection and relisting across them all?
Only Google seems to update the URL in the rankings. Altavista, Teoma, FAST, Mooter and Inktomi contine to crawl the site (at the new URL) but will show the old URL in the index for as long as the redirect remains there.
I'm not sure what happens when you switch the redirect off and return a 404, I have no intention of finding out!