Multiboxing, the process of one person playing multiple characters on multiple accounts at one time, usually by the use of multiple computers (thus the term) and macros that can be activated on all accounts by the push of a single button, has most recently seen coverage here on WoW with our 2-man Karazhan report. The act of multiboxing is one that has been the subject of some debates, mostly centered around whether or not it violates the EULA. Those in favor of multiboxing can breathe easier today, as Blizzard poster Belfaire has stated in no uncertain terms that Blizzard has no problem with the practice in a post on the customer service forums.
In short, he says that the advantages of multiboxing are no different than the advantages offered by normal grouping. Since multiboxers can be damaged, feared and CC'd as easily as separate people playing separate accounts, and since they can't do anything the same amount of characters couldn't do when played by different people, there is no reason to consider it an unfair advantage in PvP or PvE. He also answers quite a few specific questions posed by thread starter and multiboxer Velath that clarify why Blizzard accepts Multiboxing and does not consider it an exploit or an unfair advantage.
For example, he clarifies that using one keyboard to trigger macros on multiple accounts is not exploiting, but using that same keyboard to make a Fireball spell go off whenever it is availible is. Switching between windows or boxes to issue commands? Not exploitation. Using a bot program to make those windows run automatically? Exploit. In short, just like with people running one account, automation of a character via a third party program is Illegal. Setting up shortcuts to use macros or using gaming mice or keyboards (such as those in Adam Holisky's recent series of articles)is legal, and something that has always been fine with Blizzard no matter how many accounts the person in question is playing.
I certainly applaud this stance by Blizzard, even if I don't quite see myself doing the whole multiple rig setup. Admittedly, I am somewhat biased, as back in my Everquest days, I was about the only member of my small guild that didn't multibox, and was always greatly appreciative when someone when bring out their tank and healer multibox team so we didn't have to worry about who was going to fill those roles. Either way, it looks like Multiboxing is here to stay. So the next time you curse that 5-box Elemental Shaman arena team that just Chain Lightning'd you into next week, just remember that you can't call them illegal. However, you can still thank your lucky stars that they weren't Restoration Druids.