Personally I'd say the most fair way to bench would be with your own CPU for 3D, with the massive CPU dependance of today's tests. However, the current sharing rules were made so that people wouldn't have to spend a million bucks to be able to compete, and with Gulftown coming that will be the case if it's not allowed for more benchers to use the same CPU.
Yes, it can be abused, but let's hope people use some common sense;) Nothing wrong with sharing a golden chip with a couple of folks, but to pass it around the whole team is not the intention here.