Smart move by Sony, leaving it open for publishers to implement buy not requiring it for all games; that should make plenty of gamers happy, which is important for Sony, because those are most of the people who will buy the PS4; to the extent that either console penetrates the mass market, Microsoft will likely do better there.
So now the ball is in Microsoft's court. I suppose there are any number of routes Microsoft could take with this, but my guess is that it will be at least somewhat more restrictive than what Sony has done, if for no other reason than that they seem committed to the cloud. It's a tradeoff for gamers, rather than a losing situation; having your profile and game data in the cloud allows you to get access to it from anywhere, at the potential expense of not having as much flexibility with what you do with that game. The key thing for Microsoft will give gamers as much leeway as possible without sacrificing the advantages of the cloud. I'm looking forward to hearing some clear answers from them soon.