In the long term a p2p network without self cleansing is going to die, we already see lots of people complaining about Bitcoin's resource usage and performance and it is still in its infancy. If people want to use multiple accounts they can, the average user doesn't care much about it however, so only the paranoid should pay for it rather than everyone.
Who, where? Please show me one single post on the forums here about somebody complaining about the Satoshi client's resource usage or performance.