Typically, there are free tools, and premium tools available to those who pay. They could work on some new features, and only release them to premium users. Ideally, the features are only interesting to those that care a lot about their profile. Analytics are a good option.
If they charged people for any custom applications they wanted to put on their profiles, and then gave some of that money to the app developers, I could see both a dramatic decrease in crud, and a dramatic increase in the quality of apps in use (cause, y'know, they're paying for 'em.)
They should become a media company though.