Sony has to be careful how this is implemented. They cannot tick off any used game resellers in the process...
Used game resellers profit huge from used game sales and if Sony implements the serial system it would make buying used games a random roll of the dice. If Sony do implement serial numbers, used game resellers may decide not to stock Sony games anymore because they might lose a large part of their profits from this console to people that are afraid to buy used games on PS3. They have to implement it in a way theat used game sales remain or risk losing retail space.
The other thing about this is that it probably would only affect multi-player. Because, in single player someone could run a modded firmware that does not do this check so it probably can't stop piracy. This would not fix the trophy or multi-player issues though. As long as a legit copy of the game is in the drive modded PS3's will still be able to claim trophies they didn't earn and pillage multi-player offerings.
