Mazda dealer put new rotors put on my 06 Mazda 6 at 7000mi b/c it was pulsing when I would brake. Now there's 14000mi and it's starting to pulse again. Does anyone else have this problem?

 

this is known as "warped rotors". and may be caused by the following:

-using the brakes hard and immediately driving through a deep puddle of water. the cold water causes the scorching rotors to shrink rapidly where it hits. causing imbalance.
OR
-improperly torquing the lugnuts when putting back on the wheel (after a rotation, etc). Buy a torque wrench and make sure its at 80lb/ft for each lug.

hope this helps