Gregory:
Ugh. Without a clear grant we have no right to use the images
The grant is clear. In fact, the grant is more clear than the grant to license your Wikipedia contributions as GFDL. It's an agreement on the upload form where the copyright holder has to make a conscious decision to put no usage restrictions on their photo. Wikipedia, on the other hand, merely states that by editing, you implicitly license your contributions under GFDL -- a less clear grant, but I'm sure you will agree that it is sufficient.
If Wikipedia put, in its terms of service, a clause that none of its content may be used commercially without written permission from the Wikimedia Foundation, that clause would be meaningless. The Wikimedia Foundation is not the copyright holder; the individual contributors are, and they indicate their choice of license by editing. It would be even more silly for Wikimedia to do so if the pages themselves state that the content is GFDL. This is effectively what Stock.Xchng is doing.
Erik