My thoughts here are that it's definitely a good thing. I was chatting with a member yesterday who reminded of when he first joined and started to add value - we're on Salesforce and use their inbuilt Reputation system and members move through various levels as they add more value and build their reputation for adding value. He told me that it was a great driver to him as he was trying to always get to the next level so constantly looking for posts where he could add value etc.
We also publish the leaderboard (a manual process at the time but much better now within Salesforce's templates) and trying to move himself up through that leaderboard was a great motivator to participate.
I guess the thing is gamification can work.
Things to consider though is that if people aren't that way inclined, i.e. not motivated by badges etc then it's probably not a going to be succesful - however there is always someone who will try and push and then, through social acknowledgment others will see them doing it and want to be involved and recognised.
I'm waiting on my platform to have better badging, in fact any badging, that can be flexible - I'd like to be able to give badges for certain things, behaviour and value add. Also for things like attending our customer events or being a member of a User Group - it all adds to a member's social worth and perceived value within the community.