Facebook Advertising Platform
imp: I had mixed results with a small sample of about 100 paid clicks.Compared to AdSense, Facebook had 2X the percentage of users who signed up for a free account.  However, it had only half as many goal conversions, where the goal was simply using a free application.  Kind of weird.  I probably need to buy some more ads and rerun the campaigns before I make any conclusive judgments though. Costs were similar between the two.If I do PPC in the future, I'll probably do about 30% Facebook, 70% Adsense unless the conversion rates change dramatically.