For the trading out of games part, it sounds pretty exploitable. I doubt Blizzard wants to put in any resources to make a change like that to the game. It'd take artists, too. No, not on a late date like this.

And they would NEVER enable a credit card check, child check, or a monthly charge now AFTER they've released the game. It'd take out a vast majority of the game's Battle.net users, which they don't want. And since when would a game developer want their game to only have 18-year olds or older to play it? They would rather just enable parental guidance or something to allow their game to be sold to 13-year-olds. So what if some kids like that are immature? I know kids in the range 13-15 who could easily outsmart (and outwit for that matter) most people I talk to below the age of 20.

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram