I just did this on my Focus and my girlfriend's Focus as well. I tried the dental floss and it worked ok but what worked the best was a plastic spoon. Using it I got the all the letters off my gf's car in half the time it took using the dental floss on mine and I didn't break any of the letters. I didn't use a hair dryer, it was a very hot day. A little adhesive remover and it looks great!
I went ahead and removed the badges using a plastic spoon as stated before. It worked well, except the sticky stuff really didn't want to come off. I dod not use a hair dryer because it is around 100* out side today and i had intentionally left the back end of the car facing the sun. I just need to get some adhesive remover today and get the rest of the gunk cleaned up. After which i will be washing and waxing the car. I need to get the car detailed today, because I want it to look good for FOTB.