A recent thread from the Bing Forums reports one webmaster noticing 150 plus referrers from MSNBot with the referring search query of "donate." They always come from a search result of www.bing.com/search?q=donate. The thing is, his site doesn't rank well in Bing for donate. So why is he seeing this he asked?
Historically, Bing (Microsoft/Live Search/MSN Search) is known for using referral requests to attempt to find cloaked pages or find search spam. Since April 2007, Microsoft has been sending weird referrals to many webmasters. They were known as internal cloaking tests designed by Microsoft's search quality team. But even though they promised to cool it with those visible tests, it came back time and time again.
Program Manager from the Bing Webmaster Team said, "I have an idea of what's causing this and trying to fix it on the backend." What that idea is, he did not disclose, but there is speculation that these are more cloaking spam tests from Microsoft.
Forum discussion at Bing Forums.