The ebay listing has been ended.
I'm kind of a dummy - I hadn't messed around with Dwolla at all, and didn't realize how easy it is to fund MtGox that way. Nobody in the U.S. is going to be interested in a marked-up gift certificate when they can just use Dwolla.
I could always sell a certificate to international folk who can't use Dwolla, but then I'd have to deal with scummy Nigerians in internet cafes. (No offense if that is you)
OK, I take that back. Go ahead and be offended you dirty 419ers.