On Stackoverflow, I am wondering why all the members with the "Beta Tester" badge seem to have low karma scores compared to most of the others? It looks like an average of about 200 for them. Does that mean they participated in the Beta and then never came back? If so, why would they come in the first place and why didn't they stick with it? Was an initial temporary incentive to participate involved perhaps?
You're just looking at the ones that were recently awarded. The conditions for having the Beta badge are as follows:
You get the beta badge by having at least three bronze badges and an account start date prior to 9/16/08.
Most of the Beta badges were awarded on or around 9/16 of last year. The rest have been trickling in as people have been earning those three bronze badges (which is a very low bar). Seeing as they're getting to them now, it's not surprising that they aren't very active.
Here are some active users with the Beta badge: