I don't care about backwards compatibility but I do hope the PS4 doesn't have bullshit "one-use" codes like the new Xbox is rumored to have. I accept it with Steam games because they're digital, not physical, and generally come very cheap. By I'm really bothered by the idea that a physical disc you buy isn't sufficient to play the game. I miss the days when you could hold a game in your hands, these days games are just hypotheticals.
There's a thead about Sony's patent for technology with which they can restrict second hand sales or usage in a similar manner to the MS rumours. Doesn't look good tbh.