Kotaku has a brief article (and some interesting pics) about a couple who both play multiple Worlds of Warcraft characters simultaneously. Which isn't that uncommon, but the couple play a total of 46 characters at the same time. Gameslah (half of the boxing team) has a post on Dual-Boxing's forum with additional info.

I went through alot of hardware along the way. At first it was X-Keys and KVMs, then I went with Cherry programmable keyboards and KVMs. I never felt the urge to go monitor crazy -- like many boxers I focused my attention on a single screen, had another monitor locked onto another character, and finally the 3rd monitor cycled through the KVM.

If you count the number of PCs, you'll get 47. My girlfriend controls 23 and I control 23. The other one is a server. All but 2 of those pcs are diskless. It got to the point that updating 46 pcs just took too long, the hard drives added to the electric bill and generated heat, so I found a good PXE solution that works great.

[via Kotaku]