I have been using SO and I think I have over 100 questions so I am pretty experienced with it. The reward system works pretty well except of a few drawbacks from usages for the sake of gaining points:
1- To fend off bad/half-assed/useless/irrelevant answers, my questions tend to be specific and include as much information as possible. If I am looking for something specific, I post very specific requirements. I get answers from people who seem to just Googled the question and did a copy of paste. Their solution is far from satisfying the requirements. Example: I need a network sniffer that does this and this and this and this. I get a flood of 'WireShark' recommendations just because its a popular product. Do they ACTUALLY know it satisfies my requirements. NO. They mention it just because they HEARD its good.
2- I get an answer. It gets one upvote. I leave a comment indicating it actually doesn't answer the question and I leave a reason. You would think people read the comment. No. The answer gets a lot of subsequent upvotes!! Upvoting for the sake of upvoting and getting points. Then the question doesn't get anymore answers. I guess users think if an answer has many upvotes, it must be the right answer? No it didn't and I mention this. and then the question loses steam and no one bothers offering more help. Frustrating.