UberCPM

You can consistently garner a few dozen or more impressions from running their safe ads on your sites but that's the only good thing I can say about them. They recently went from letting you cash out upon accumulating ten bucks in your account to making it so that you must earn 25 bucks to request a payment. You can easily get up to 1000 impressions and still have no money in your account balance. On top of that, you can get multiple clicks and not earn one cent from that.