There has been several accusations of referrer spamming made against Microsoft in the last few weeks.
According to Wikipedia, "the technique involves making repeated web site requests using a fake referrer url that points to the site the spammer wishes to advertise. Sites that publicize their access logs, including referrer statistics, will then end up linking to the spammer's site, which will in turn be indexed by the search engines as they crawl the access logs."
The problem is that too much of those request amounts to a mini Distributed Denial of Service and can cause legitimate users to be left out as the websites flinch under the demand.
The keywords used by the referrer - in this case a valid Live.com search - often has nothing to do with the page which it visits and look as if they were generated by a Spam engine.
One webmaster says that it is a deliberate attempt from Microsoft to increase the number of Live.com referrals.
However, there has also been reports that these spam referrers were caused by someone abusing Microsoft's Tide Proxy Servers, rather than a deliberate attempt by Microsoft to cause harm.