The official Microsoft representative has told us in a WebmasterWorld thread that it has been shut down. He said:
I just spoke with the team. They said they are working on a fix for this, but the feature causing the problem is turned off currently, so you shouldn't be seeing any fake referrals from us.
Exactly what type of "feature" is causing this to be a problem is not clear. In the past, we know Microsoft had a bot that tested for detecting cloaking. But this time, the Microsoft representative did not mention cloaking. Is this some new type of feature or just issues with the old cloaking detection algorithm?
Forum discussion at WebmasterWorld.