OneAndOneIs2

I had a vague suspicion that it was a spam-bot trying to give fake referrers via search engines rather than a genuine search bot.

Looks like Microsoft are really shooting themselves in their PR foot.

I can think of another reason you might do this. Not that I'm making any claim this is why it's being done of course.

Some sites pick up search terms, and change their output to try to match the search term, essentially by being a dynamic link farm. So they then appear to be more relevant than they are, hence get more hits. It might be that Bing is trying to detect these sites and remove them from their index.

Of course, that would be a great idea, so it's probably not the reason ;-)