A thread over at HighRankings discusses a possible bug with Yahoo! Search and MSN Search in the way they handle the 301 redirect.
The issue is as follows:
Conducting a search on Google for hyatt regency dearborn brings back the URL "dearborn.hyatt.com".
However, conducting a search on the same keyword phrase at Yahoo! Search and MSN Search both bring up the wrong version of the site, "highlands-inn.com".
One member says "I believe I heard something about this issue on Yahoo where they haven't implemented (bug?) the 301 properly, meaning they don't take the original out of the listings like they should. I'd imagine you'll just have to wait until they fix that or contact them and pester them to make it happen faster." And a moderator and frequent SES conference goer states "Yahoo admitted that was a bug they were working on at SES. I'd wait it out if possible."