Is it ok?
With various bans for a variety of different things going on many players have been getting worried about their dual-boxing playstyle. I know several players in my own guild that multi-box. Thundgot from Blizzard stepped up and had the following to say over the weekend.
We have stated several times that we have nothing against multiboxing. As long as the player controls each of the characters the player may run multiple clients/characters.
We're aware of some players not agreeing with us on this - on some topics people simply have to agree to disagree. At the same time, expressing disagreement in a nice way is of course no reason for jumping on someone. Constructive feedback and discussion is always encouraged. :)