It's all about profit. That is, when the transactions are all said and done (whether the user paid for the service, or the advertisers have bought their advertisements) how much good will is left over?

How much good feeling does each party how? Can the user say that they feel good about using the service, is the service provider satisfied with how the transactions lay?

With Facebook and twitter some people, users and advertisers alike, don't feel enough profit from the service. Maybe with App.net they will.