TheMadScientist - 7:45 pm on Mar 17, 2011 (gmt 0)
Most likely because the title text appears in a link to the page somewhere.
When they can't crawl a page they take whatever resources they can find and try to figure out what it's about. Example: If there are 10 links to your page across the web and 7 are unique, but 3 are your title, the most likely text for the page is the title of the page ... If there's only one link and that happens to be the title of the page, then that's probably the title they're going to use for it.