been saying this for ages.
the biggest problem is that the store, and the actual distribution and management system are intertwined. I dare say the same is true for all the other competitors too tho, so they can pipe down!
the problem is, you should have one log in. one client. one collection of games, one friends network ect. and you should be able to buy from ANY online store, NOT just the steam store. the "Store" and the "distribution/client" methods should be INDEPENDENT. I'm not even saying there should only be ONE client. Ideally, you would have many clients, and many stores that were all interchangeable as they all used the same packaging and distribution method, obviously controlled by an impartial 3rd party. as it stands, the store bound to everything else is anti-competitive. hell, even with the itunes store, you don't HAVE to use itunes to play the music, you can export songs in and out. allowing you to use the store and the itunes client independently.