I guess what happens if someone is able to hack all the accounts...?
I think it would sort of suck for someone to completely take over the Bitcoin network and have all the money with no way of reversing it...
At least banks now can reverse transactions so that can protect your money..
I don't think you really understand how Bitcoin works, you can't "hack" all the accounts. You can take over the network with a 51% attack (see wiki for details) but that's not something that would have to be permanent.