I've never seen any like that on this site... But on a couple of other sites I've encountered them. Yeah, very annoying, especially when they just redirect you to the main page and make you lose whatever you were doing (writing a message and losting all the text, clicking a link and ending up on the main page)... Is it like that here, too? Losing messages and all, I mean?
And of course the worst thing - not to me, mind you - is that the ones I've seen on other sites have been ridiculously badly designed and not functioning too well, so that I don't even remember what I've skipped. I'd call that inefficient advertising.
But again, never seen it on this site. Pretty weird actually, since a few people have seen it but some haven't.