A small number of individuals amassing enough hashing power is a bad thing. Crypto currencies are, at their core, about decentralization and trust. Even power split between a few entities can represent a threat to the system. Thankfully the system has other means by which it deals with this: alt currencies.
This is just the beginning. Nothing is slowing - it's just changing form. It would be interesting to overlay the amount of Bitcoin being bought with alt coins.