Nah Blizzard EVEN did a interview with a guy pvping with 5 PCs...as long as its 5 accounts with 5 PCs its legal.
I can effectively multi-box with 3...1 tank 1 dps and 1 healer. Single rig and I abuse the hell out of my Alt+Tab key.
thats not exactly multiboxing, it only is if you can cantrol all chars at the same time
