I have the same issue with my car now at just over 10,000 miles. The tires were cupping really bad on both the outside and inside edges of them in both the front and back. I have rotated them twice since the car was new. I had it in to the dealership last week and had it aligned, balanced, and rotated. Still make a shitload of noise, but I'm hoping that it was just out of alignment and that maybe the tires will start to wear down a ittle more evenly and the noise will diminish after a couple thousand more miles.
If not, I will be off to buy some new tires because I cannot stand that noise. It is irritating as hell. I WILL NOT be buying the same crap tires that came on the car new!
2004 RX-8 Titanium, 6-spd, black/chapparal, GT pkg, no nav
1991 RX-7 convertible