Been experiencing the same with my blog Optimize Your Web: Optimizing and Internet Marketing search engines and people. Seam to be nearly random one word search phrases and when I test I can't find my site as a result on the top 100 for most of the phrases. I posted an article on this some weeks back Microsoft counts for 50% of my blogs visits | Optimize Your Web and another back in June Is Microsoft testing Live Search? | Optimize Your Web on this topic.

I have used Indextools quite well to monitor the organizations coming in and Microsoft.com has a big portion.

Might also want to point out Mel Carson's post on the topic Microsoft Opens Search Technology Centre In Europe | Mel Carson - Internet Marketing Blog - Microsoft - Memoirs