Ha, K.C. beat me to it!
I didn't use a hair dryer. My 4R was out in the sun and the letters just popped off one by one. The badges on the rear lift gate gave me a little more hassle, but I just parked my car so the back was facing the sun for about 15 minutes then I was able to get them off as well.
The badges on the side did not leave any of that sticky stuff behind. We just clay bared it, put on some paint cleaner (did that on the whole car while detailing it), then waxed it. The badges on the side, however, left a a lot of that sticky stuff behind. It took a little more work with my finger nail and some rubbing alcohol but eventually I got that stuff off and followed the same procedure that I did for the sides. You can't tell the badges were ever there. Looks much better IMO.