In my point of view this can't be called opening. This is the method of utilizing other people's applications within their own platforms. Those sites can't be called opening platforms. The users have many kinds of demands. And they often satisfy their demands by visiting other sites. But with those so-called opening platforms they let other people to develop the applications based on their platforms. And they can get revenues from this. On the other side those applications can't work without those platforms. This is just making use of their advantages in one way. To be extreme those platforms can be called monopoly.
This way of opening platform can't work well. This is just the change of tactics. They just do other things in the name of opening platform. And this kind of opening platform hasn’t solved the problems of equal game.
Regard of the platforms, no matter the real opening platforms or the platforms just in the name of opening, the users are all opportunists. They don’t care whether the platforms are real opening or not. What they care is that what they can get from the platforms. Zynga and Rovio are all opportunists.
What are critical to the opening platforms are the opportunities that you provide for other people to play games on your platforms. The users number scale, users relations and the economic system are all important.