How is iAd different from say, Facebook or Google, except for the vast amount of data collected across sites, platforms and services by these companies? Don't F

How is iAd different from say, Facebook or Google, except for the vast amount of data collected across sites, platforms and services by these companies? Don't Facebook and Google also match the user profiles that they create/manage with their ad inventory and display targeted ads? They're not really selling your personally identifiable information to advertisers, but instead provide only aggregate data about the reach. The advertisers have to trust Facebook or Google too for the matching. [I'm talking purely about what these companies do, and not about malicious sites and other ad networks or about how safe the personal profile information really is.]