Assuming you are able to do this tactic without being killed by guards/other players...
Essentially, the only time Blizzard would step in is if you took it too far. Camping someone for several hours, for example. That falls under harassment and would earn you a ban.
A few kills in a row would be fine. Of course, you also have to remember that as soon as you unstealth for the second or third time, people will be watching and waiting for you. So I doubt this would work in your favour anyways.
Multi-boxing is fine, ganking is fine. It's only the harassment issue, and that would only be after a few consecutive hours of camping.