I love badges. I like the TA ones, but I wish there were more. Rather than gold star / volume based contributions, I think there should be a whole range of badges for people to get. And what could make it even more fun would be to not even know how to unlock them. (yes i know Foursquare does this particularly well.)
Helpful reviewer badge: 10+ helpful votes
Frequent flyer badge: self explanatory
The high life badge: 10+ reviews of $$$ locations
Budget traveller: same thing, reversed
Angry / Happy reviewer badge (for having too many low or high score reviews
Badges are supposed to be fun. It's not a case of contributing 50 bog-standard reviews just to get a gold star, you're here to share your knowledge and experience, and this could make that fun. Not only that, the badges should give an idea into the type of reviewer you are.
At the end of the day, all Trip advisor wants us to do is provide honest reviews of the places we've been to, to benefit others.