I don't blame anybody who thinks it's not as regulated as it should be but you might be surprised at how extensive the current requirements are. Storing ~200 million daily transactions in order to fulfill arbitrarily complex reporting specifications from SEC, FINRA, internal audit (rogue trading detection, etc.), not to mention analytics for other trading systems... Oracle/IBM/whatever enterprise big data provider gets the contract must be sending one gigantic fruit basket around Christmas time.

EDIT: Here's a little light reading for you http://finra.complinet.com/en/display/display_main.html?rbid... (or you could just take sandpaper and rub it against your brain)