OK, thanks for clarifying.

I can see where double-voting is a problem, both for official votes (e.g., karma-counts) and unofficial ones (e.g., discussions on controversial issues).

I can also see where people lying about their actual demographics, experiences, etc. can be problematic, though of course that's not limited to sockpuppetry. That is, I might actually be female and Christian, or seventeen and Muslim, or Canadian and Theosophist, or what-have-you, and still only have one account.