I agree with whats been said before - signatures tend to add too much clutter. If you can enable a short (200 characters or less) PLAIN txt only signature then maybe - but even that would start messing up the joint.
Maybe if only senior members+ had it and there were restrictions on what can actually be put ina sig - then yeah, otherwise don't see the point.
i.e. Don't let people post images / links (to other sites) in their signatures. (Links to threads here might be acceptable)
Personally, my signature would simply be a line and my nickname (something like this:-)