Yes, I can understand that they're wanting to maximise revenue, but I'm sure that some levels are fixed so that they're physically impossible unless you play them over and over or buy the fecking cheats ( which I refuse to do).
Angry Birds is hard on some levels, but at least you have the same scenario and birds each time, so you don't have to wait until an achievable bird scenario comes along. This game is pissing me off now, because I'm sure they deliberately give you unsolvable combinations most of the time.