Many sites have turned to Flash as a means of circumventing popup-blockers and selective ad-blockers, relying on the fact that most browsers don't have the ability to turn off Flash on a per-site basis. If you've got a popup blocker installed but still see popups, that's why.
Flashblock is a Firefox/Mozilla extension that provides easy and free Flash blocking on a per-site basis so that you can keep Flash switched on in Flickr, but turn it off for sites that use it to spawn popups. Link (Thanks, Doug!)
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.












