I think you underestimate how efficiently bricks render, and how inefficiently these wires would render considering they probably have physics.
Well, it should probably only be about as bad as emitters, at least by the look of it. I wouldn't think they would need to use physics, especially since they don't collide. If they way they are rendered is that hard on a server, though, I would keep people from overusing them, or somehow have the use limited to a level of admins.
What Squideey was pointing out is that anything can be spammed, and it's a matter of keeping it under control, not trying to prevent the possibility.
