I have a 2007 ES350 and have had the same problem 3 times. First ~10,000 miles, then ~30,000 miles, now at 49,800 miles. The dealership turned both front and back rotors the first 2 times. I requested that I get new rotors under warenty due to the hisory (and the fact that my warenty is over in 200 miles). The delership agreed, thank goodness. I should pick up the car today.
I do feel lucky since I was denied all service at a dealership near my work and told to go back to the dealership near my home to work out something. I wa not happy - I am slamming that dealership in their little customer feedback card....