I realize the article I posted previously was a weak arguement and not entirely convincing. This has gotten me fired up and in the spirit of getting a definitive answer I've been doing some research. From what I can find in my short search, the veterinary science community is not very concerned with sporting canine dew claws.
I did find an article in Dog World by Caroline Coile, PhD. The official source is: Dog World; Jul2005, Vol. 90 Issue 7, p18-19, 2p, 1c
While there is no hard data to back it up and it is more of a discussion paper, there is a section in this article dealing with the dew claw debate from which the following excerpt was taken.
Should you do dews? Most shorthaired show dogs have their front dewclaws (which, technically, are not dewclaws but simply first digits; dewclaws are just the ones on the rear legs) removed simply to achieve a cleaner line to the leg. Dogs can snag and rip out dewclaws when running, so many breeders also do it to prevent injury. The propensity for injury seems to depend on how floppy the dewclaws are, with those that fit more snugly being less likely to snag. Many owners of performance running dogs contend that the front dewclaw is an important part of a dog's running gear. They point out that these digits are attached to muscles and ligaments that, when cut, no longer have a point of attachment, potentially weakening the wrist area. They also point out that these claws contact and grip the ground when running and turning at speed. The jury is still out on whether removing them is for better or for worse.
I think the last sentence clearly points out that neither side has a stronger arguement in the debate. Take from it what you want. If anyone else has a better reference it would be great to see. Until then it seems to me that either side of the arguement is equally valid.