If people like a game, they will pay for it as long as you don't have some kind of annoying obstacle preventing them from doing so.
edit: DRM isn't even really a good counter to piracy for the most part. It will be cracked sooner or later (sometimes before the game is even officially released) and the people who wish to pirate it will do so.
(Which is exactly the value point I'd be working to improve if I was working at Steam and trying to convince more titles to release there.)
* http://www.reddit.com/r/Steam/comments/1j4lj3/how_doesdid_st...
Steam lets players join multiplayer games with their friends -- seamlessly merging a friend list with game servers across all games. That's a strong incentive to use Steam.
So what about other forms of content without online multiplayer like say, TV shows?
I.e., 100k paid sales and 10M "unauthorized copies" is still enough for an indie dev to make a living.