If Tazmo requires two servers for only 30K members (sure it can jump up but its wont break 50K) then he or whoever is managing the servers sucks completly.
Many forums I visit that have 50K members (not counting non members) on a regular basis are only on a single server.
Second, No host would shut down a dedicated box for too much bandwidth usage, heck you CANT spread bandwidth usage. Unless hes renting a data line and puting his own machines on them, each dedicated box you purchase from a host gets its own bandwidth once this cap is reached the box is taken offline.
Even colocation follows those rules, they give you a certain amount of bandwidth per rack that you rent, every extra rack you rent gets its own bandwidth... they are not shared.