-1, all my points have been described already.
Obtaining any amount of money should be an inconvenient process, as that makes the end result more rewarding in the end. By allowing spawners to be accumulated, exp and miscellaneous mob drops will have their values reduced to a minimum. Not only will this ruin their respective markets, they will also cause other products to lose value (ie. enchantments, wool, emeralds). While it may seem like it would allow more people to create things such as god tools, one should keep in mind that, if anyone can get their own set easily, there is no point in buying/selling any of those tools. It is already easy to get a decent amount of exp (as proven by various /pwarps), and it shouldn't get any easier.
