Just to nitpick, the post you linked to by Ian Hickson does illustrate how DRM has been used to limit functionality, but both your post and his doesn't explain why "copyright protection" is a straw-man? I don't believe it is a fair argument to say that copyright protection and whatever functionality they enforce or prevent by use of DRM are mutually exclusive.

Although, I do see the point that some parties could hide behind the "We need DRM to protect our copyright\prevent piracy" flag and instead use it to lock-in consumers and build a walled-garden.