An old housemate of mine used to dual instance eve on his machine. To be fair it's not even in the same league as dual boxing with wow and other similar mmorpgs. You can leisurely switch backwards and forwards using alt tab easily... although I guess it could get interesting if you are dual boxing in fleet battles and stuff in 0.0, but I reckon you'd be less use to your corp in that situation anyways. In short though it's generally a lot easier to play two accounts at once than wow, and a LOT more people do it.