I figure if anything were important, people would put it in the body of the post.
I am probably missing out on some interesting or fun signatures, but that is a sacrifice I can live with. I saw too many long and worthless signatures, so I turned them off.
There's nothing witty or humorous about my sig. It's probably close to the too-long border, (if not across it). But I also try to avoid trivial, spammy, posts here on the message boards, so my sig is not hanging around everywhere.
As for other people's sig, I've many times found chuckles or information in them. So long as the sig isn't consistently longer than the poster's post, I think sigs are fun and good.