Since Steem is a decentralized network there's really no way to control people having multiple accounts. Anyone with an account and some STEEM can create additional accounts, and no one has the centralized authority to stop them or demand phone number verification first. The idea is that each account has to have something invested in it (SP) to have any credibility.

I agree that voting bots should die, but given the above the only way to accomplish that is by fixing the economics of the system. I think reverting the vesting schedule back to 2 years like it was originally would help, and I also think there should be curation penalties for voting against strong consensus. A long vesting schedule should make massive whales less abusive since they know their behavior can have a real impact on the value of STEEM over two years, and curation penalties should make smaller fish think twice about sneaking themselves rewards by voting up their own spam.