I'm in the prewashing group, so I haven't experienced fabric shrinking in front of my eyes! It's interesting to note, though, that the fabric didn't shrink evenly - that is, it was still 6" in one direction, but not the other.
I often use starch after I prewash, but like justwannaquilt, I starch BEFORE I cut, not after.
I personally don't think it's complaint worthy - cotton fabric is known to shrink, so you really do take a chance if you use it without prewashing. It's not the fault of the LQS or even the fabric manufacturer - it's just the nature of the fabric.
I did report back to my LQS regarding one fabric - it was a beautiful deep purple floral. When I washed it, it bled. Same thing happened the second, third, fourth, and fifth times I washed it! At that point I decided not to use it, but I did let the LQS know about it so they could warn others to use necessary precautions when using that fabric in a quilt.