It would also be a good idea to limit memberships to only 1 per person.

This is a non-trivial problem.

Many users have access to hundreds of machines with unique ips and have the scripting resources to automate nearly undetectable sock-puppets.

The one thing they can't fake is steem. So, under the current system, they can't amplify their vote with multiple accounts (well, except for the free steem delegation and (25) rep that each new account automatically gets, which is sort of a problem of its own).