Yes. With this system it would be important to verify identities on sign up. I think verifying phone number would largely resolve the issue (SMS short codes don't work on VOIP phones). There many other levels to reduce fake accounts that can be added if problems begin to occur.

The main issue is the more difficult sign up is, the less people sign up. It's a balancing act.

With any voting system you have to detect the validity of the votes, even upvotes.