There is a WebmasterWorld thread where folks are reporting that MSN Search is indexing a bit too much. Reports suggest that MSN is crawling and indexing the content found on pages which are excluded via the robots.txt directive.
Normally, if a search engine crawls the page, they may only keep the URL in their index but not the content.
Moderator Receptional adds, "My examples show no snippet. But I can get them by typing unique text into the search query."
So if they are returning results for text found on the page, maybe they are indexing a bit too much?
On the other hand, I have a thread at Search Engine Roundtable Forums suggesting MSN doesn't index enough, specifically new sites...