It completely removes the purpose of the archievements?
There's a third party program that you can use to unlock steam achievements (at least it used to work, I don't know if they fixed it from working) that I used once when TF2 weapon unlocks were tied solely to achievements
But few people even used it, instead you had a ton of achievement farming servers
Achievements could work well as an incentive to do positive things for the community though.
In theory, like you could have an achievement for uploading an Add on and having it get a certain amount of downloads or a high enough rating. But I can't think of more than a couple examples of similar things that would be easy to detect.
