There was a report yesterday of domain hijacking, which proved to be a little bit less heinous than that but no less annoying.
It’s a third-party script, which apparently piggybacks onto the existing SiteMeter code. Fortunately, it was easy to identify. If you’re using some form of ad- or popup-blocker, this is something you’ll want to block:
If you’re not, well, why not?
(Hat tip to @GLHancock, who saw it here first.)