Duh?
It amazes me that the folks that design this stuff could look at popup ads and say with a straight face, "Oh, yeah! The visitors to our site are gonna LOVE this!"
I guess some people are just stupid.
Some webadmins are lured by an easy way to generate money for each click from their website, but some sites become so convuluted with pop-ups and redirects that you can't even reach their homepage. I don't know what these people could be thinking, ultimately the best way to generate money from the web is to offer a legitimate product or service and work hard at attaining rank in the major search engines. It's harder to do, but it will ultimately lead to more stable income and keep you from attracting the interest of lawyers- which will be increasingly likely in the future IMHO.