When I noticed the vox populi badge, not long after after creating my account, I decided I would try to get it, since I had some free time.
I took an extended tour of Ask Ubuntu and found 40 really great questions and answers deserving my upvote. I learned a lot that day!
Now on some days I still use all my votes, because I spend a lot of time exploring and testing, and finding posts that deserve them.
So I think the badge served its purpose in my case :)
I think, in general, if people care enough about the site to want to get badges, they will most likely care enough to vote in good conscience.