There is no problem with that. Take the clan, "The Dark Reapers", for example.
Though keep in mind, if you do this, not only will you be regarded as 'cheap' and not original... But a loser as well. People within the realm are mean, and all that good stuff. If you're easily offended, then I suggest not to do so. Also, trying to remember all of their passwords, well, could be difficult.
And another thing. I am sure that I read somewhere in the F.A.Q., that you cannot make any contact with alternate accounts in-game. So, it may be against the rules. The reason why I say it might be fine, is because I see it happening in-game, and, well, nothing is done about it.
