Rewarding good behavior has its place, but as I mention in this answer, I believe that children should not be generally rewarded for meeting basic expectations.
We use positive feedback as a crude form of reward for my 21-month-old son; cheering and clapping when he does what we ask him to do. However, we don't bribe him with incentives (no "if you pick up your toys, you can have a cookie", etc.), and as he gets older we plan to simply communicate our basic expectations, and enforce them without a reward system.
We still haven't decided on what route we'll go as far as money/allowance/etc., but I'm leaning towards a system that rewards exceptional performance, as opposed to meeting basic expectations.
As I mentioned in comments to that other answer, I believe it is a parent's job to teach children the lessons they need in order to be a good adult.
Offering children rewards for completing chores and basic tasks teaches them that they should expect rewards, and that tasks or chores that don't result in a rewards are not worth doing. It leads to a sense of entitlement, which leads to frustration and disappointment later in life when they learn that that is not how the world really works. Yes, they will get "rewarded" for doing their job later in life with pay, but more and more people seem to believe that getting paid for their job only requires them to do the minimum required by their job description, which is not a healthy attitude in a competitive marketplace.