They're image ads...and they're not really popups, It's Flash and expands right in the screen.
That's why I use Contextual Text Ads - It pays better.
It's a pain, but I'd rather the advertisers pay and not me lol.
Actually you don't pay, Per Click, Per IP = Money and they have too be unique and if so it means cash.
Google, Inc. pays MonroeTaks per Month (As long it's $100+, Unless they setup their Google Adsense too hold their earnings.
I've made $900 per Month of Ads so it's nice extra income.