Badges are, simply put, another system of rewards. They offer feel-good rewards for any particular task. They seem very similar to individually wrapped peppermints that are thrown across classrooms for correct answers. The real questions in life offer no peppermints or badges. Real, authentic efforts to improve oneself should be reward enough. There are very damaging side-effects that come from extrinsic motivation such as badges. People come to expect reward for any task and will not complete something if there is no reward. Learning should be intrinsically motivated because the learner sees the value in learner a certain skill or content not in order to receive a reward.
@MisterEason via http://justeneason.com/2011/09/24/we-dont-need-no-stinkin-badges/