Social Application and Social Widget Advertising Integration

So was just having a random thoughts while designing a couple of social applications. I was thinking out you can build social applications that run on different platforms and work with a web service that allows various information to drive the application.

So why can't you start evolving advertising to be widget based and run more like application. They would feed from any demographic or targeting data you would have on the user and feed them an intelligent and interactive ad.

Just a random thought. Will someone please do it for me.