Rewards for Involvement

I've had a think about a discussion from last night about adding an element of "status" or "badges" depending on how many reviews or surveys a user has done. I was initially resistant to the idea as I thought it might produce an unhealthy element of competition in what is ultimately a remarkable example of a group effort. I thought about other web based things I'm involved in and I've realised how much I'm motivated by reward schemes (eg learning a language, consecutive days and words learned a rewarded by stars or levels). So I'm now thinking that maybe something that rewards involvement at a low level (reward of badge or stars for 1st review or survey then 5th review or survey) could get someone involved or more involved to the stage where getting the ways walked and the reviews done becomes more of a reward in itself. I'd want it to be a means to encourage the more casual volunteer to get involved rather than an exercise in saying "ooh look at me" so I'd plateau the rewards at say, 20 reviews. Thoughts?