Yeah, if you take it seriously, have the funds available, or as in the case of the VCFA administrator, receive donations, then a powermac would be a suitable server.
I've actually been thinking of grabbing a G4 or G5 running debian Linux, Leopard or Leopard Server to replace tacgnol (the laptop server I've got right now), as a more robust solution, although that is borne very specifically out of my own personal desire to run old, ancient, mostly unsupported, proprietary UNIX platforms.
I also have a pentium dual-core system that I may put back in the server role, where it was before I realized that it's really more horsepower than I need right now, but I can easily mirror the dual 750gb disks in that machine, and use it as a backup server for whatever other machines I have, as well as just web/shell.
Anyway... not everybody who is willing to run something like the VCFA has a P|DC box hanging around, or even a powermac G4 that they can just drop into service. And likewise, not everybody with G4s and similarly powerful machines is willing to run an archive like VCFA. (I have the computational horsepower and the bandwidth for it, but in a round-about way, I work for my ISP and am unwilling to host anything that might break our AUP, and thusly get me fired.