The big issue with game servers is the upload bandwidth.
A lot of consumer accounts (both cable/DSL) are only
128kbps uplinks.
That's enough for about *3* people outside the house to
connect to the game server before you'll run out of
bandwidth. (Different games may change that to as many
as 5 or as few as 2.)
Basically, take your upload bandwidth (128kbps) and make
the broad assumption that each client will require
48kbps (could be as low as 24kbps or as high as 56kbps).
128/48 = 2.67 users.
