AFAIK the Prusa Mendel is a type of RepRap. If you were to group them together then that would make the RepRap a close third.

I've taken my Solidoodle along to the local hackerspace on occasion, and I tell you that it was always well out-numbered by the various flavours of RepRaps being assembled, worked and debugged there. The whole thing about printing the parts on another machine is very attractive to the hacker community.

The inclusion that I'm most surprised about is Zcorp. I'd have thought that those machines would have been sufficiently unaffordable to keep them further down the list, but then again I suppose they have been in business quite a bit longer than most of these consumer-level machines too. I can't see the situation lasting too long though.