The next step is only selling half the game. And then making the second half only available if you paid a premium
That's a slippery slope argument, and it's the same as saying legalizing gay marriage will some day lead to the legalization of human-animal marriage.
Now, here's my question: companies like Stardock and CDProjekt are heralded for their consumer-friendly approach of "get things for free if you register the game". Explain to me how the practice is different - you can play TW2 or Sins of a Solar Empire without registering your game, but you lose access to any patches or other content available for the game.
In essence, both are anti-piracy schemes that provide the player with additional content. People seem to hate online passes, but they seem to love the type of schemes that the aforementioned companies put forth. I don't see a great deal of difference between the two.