I don't think we can expect "perfect" anytime soon. Telltame games has something like that. An online activation before you start playing, and that's it. Plus you have a high number of activations (25 or something) and it doesn't need to be on the same computer every time. That's good enough for me.
Warcraft and Starcraft would never have been so popular if it weren't for 'piracy', by the way. More people should see the marketing power of a little unlicensed distribution now and then.