Rewards for positive actions have a few side-effects that I have observed though:
1) Individuals start expecting positive reinforcement for everything they do. Doing it for the external reward instead of finding the intrinsic reward for doing the right thing on their own. This is probably extensively researched already, although i don't have sources handy right now.
2) Along time, positive reinforcements behave in accordance with the "law of diminishing returns". i.e. If you always reward positive actions with some standard reward, it will lose effect over time. With the danger of the positive action not feeling worthwhile anymore.
I thus became a great believer in the importance of negative consequences for bad behavior. I mostly apply (within reason) Shame and Restriction of freedoms to punish my kids for bad behavior (reserving the occasional physical slap for very serious offenses). Shame is a motivator that interests me a lot as a parent. I think it is an essential motivator in society in general, but the most delicate one. Too much Shame can also make you socially inept.
In the end I think its always about the right balance...