I do, I also sprayed some WD-40 on my mtn bikes squeaky disc breaks
It baffles me how many people misuse WD-40 for lubrication. WD-40 is not a lubricant, is it a solvent/rust dissolver. It lubricating properties are poor in the first place and on top do not last very long.
Clay, if you have sprayed them with WD40, the pads need to be replaced...clean everything with a spray can of Brake cleaner and put new pads in. They should come with a type of "lubricant" to apply before instalation to keep em from squeaking!
HKTRDR is right, its not a lubricant...while it helps initially, it will only worsen the problem in the long run as dirt and dust will stick to the fluid.