Dont forget about nofollow on signature links, to me that's pointless.
They way I look at forums is that if I scratch your back then you should scratch mine and other members. In other words, I help to put valuable content on your site so the least you can do is allow me to have a "followed" link in my signature. I've had this debate before with some people and they tend to think that my thoughts were odd but when you think about it, posting in forums takes time and time equals money, so...
Oh did I forget to say, thanks for the links Lisa - they are appreciated.