I personally think it's a great idea.
SitePoint, a forum about running websites, does this. They have special badges for helpful members, like "SQL Guru" and things like that.
I think it's a good way for people to see who gives good advice and is knowledgable, rather than reading two pages of an arguement to see which person comes out as knowledgeable on the subject.
As long as they are AWARDS and not REWARDs (ie - there should be no contest for them, any number of helpful members should be able to get them [not just one person per category]).
As long as it's not a contest, people won't feel cheated. If members prove to be very helpful on a particular subject, they should be recognized as such, and I don't think it should require reading everyone of their threads to recognize that. A nice little badge under their avatar would be great.
It encourages members to be helpful and polite, and at the same time, gives members (old and new alike) an idea of who's got good info on the subject.