Appengine lock in by design, not a strategy.

Though lock-in is not the strategy, it created the same effect. Not sure why, Google routinely gets a pass for these kind of things. The one true open (its a bit debatable as well) software they did was Android and that is pretty much it. They've taken bunch of unpopular decisions in recent history that affected developers/users. Maps pricing change, Google reader, decent Api support for G+, etc.