A great excerpt from a recent book by Laszlo Bock "Insights from inside Google: Work Rules!"
It reminds us that creating a healthy competition between teams or individuals can be a very effective way to motivate people to excel:
What did work was creating a quarterly survey of just two questions:
1) In the last quarter, this person helped me when I reached out to him/her.
2) In the last quarter, this person involved me when I could have been helpful to, or was impacted by his/her team's work.
Every member of the team rated each other member, and the anonymous ranking and results were shared with everyone. People knew where they fell in the ranking, but didn't know where anyone else fell. The two most obstreperous people, of course ranked near the bottom, and were dismayed by it. [...] Though not strictly a nudge, this was in line with work showing the power of social comparisons.