good Idea, how would it be hosted? I host a small mc server on ~1Mbps Upstream and it starts getting laggy at around the 5 player mark, so bandwidth will be a problem, perhaps running a virtual server on the amazon ec2 cloud may be an option which can be relatively cheap, but again it depends on how many people are interested as to what kind of server loads and costs would be, as I said before, I personally don't have the kind of resources needed to serve more than about 5 simultaneous users (due to crappy net speeds).
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Arch Linux x64, P8400, 4GB PC-6400
Ubuntu Linux/Win 7 x64 X4 955BE, 12GB PC-12000, GTX 570