Ugh, don't remind me of.... her *shudder*
AI is the primary offender(as I still go there quite a bit, mostly to read, and laugh at the political flame wars) But it has also happened on MacNN once or twice, and it did happen at least 2 other times during my internet browsing of the day, though, since the pop-ups tend to hide in the back, I don't always notice them till I've left the site, and no, I'm trying to cover my tracks from all the porn I don't look at.... aw crap.
seriously though, I was looking for some ROMs today, and those sites are full of crap... that affects windows users, it's a sad day that it troubles my OS X paradise.
On a side note, it would be a pretty funny prank to pull to have a message play upon entering the site "Hi, My Name Is TINA!" just to give us old-timers all heart attacks
But the fallout (posts in suggestions, genius bar, general discussion and AO saying "OMG TEH WTF?!") Might be a little much.