Since August 2007 Microsoft has been sending out weird referrer data to people's log files. The spam like referrers were official cloaking tests from Microsoft and should have been resolved in 2007. But they came back in January 2008 and then again in July 2008 without explanation.
We are now seeing them again, starting last month. A WebmasterWorld thread said it is coming from search.live more than MSN bots.
Microsoft's Jason chimed in the other day suggesting Betsy Aoki at Microsoft via this form. But soon after, Brett Yount from Live Search's Webmaster Center came in as MSNDude and said:
I would like to apologize for the inconvenience this is causing. We are working to correct this issue ASAP.
Hopefully it will get resolved soon and forever.
Forum discussion at WebmasterWorld.