Devs are not forced to develop for it. You can go develop for Android. You can go develop for RIM. You can go develop for non mobile phones. Devs develop for the iP* because they want to sell to that market. It wasn't too long ago though that we saw a whole bunch of articles on HN about the myth of the get rich quick AppStore apps. Apple is skating on thin ice because if the developers leave then the iPad loses big. The pain may not have crossed the average developers threshold yet but Apple still has to play a dicey game with how far they can go before they do cross the threshold.