Nice to see that im not the only one with only a single core processor as my main workstation!
Think it will be interesting to have seem how this kind of a poll would have gone in a more windows orentated forum. Apple has been using dual processors in their mainstream products for longer than for example dell has.
When you think that virtually every Mac laptop is single core and add in all the eMacs, PPC iMacs and Mac minis, it's really not surprising. Post the vote again in 12 months time and you'll get a big difference in the answer.
I voted one, as I "only" have an iBook G4, and I guess that answers the intention of this poll, but I'm pretty sure there are more CPUs in there, dedicated for different uses, like the Firewire controller and GPU to mantion a few... so the hones answer should have been: I have no idea.