I think it's a great idea, paid signatures add nothing to the site and only encourage useless posts. There are way too many people who post in every topic because it gets their post count up, the posts look useful but overall it really just adds to the noise.
Good luck getting glorious leader to make a change!
Will link Theymos to this thread if I ever see him on IRC (which is rare).
I'd like to see people only advertising their own stuff (for sale, for free, advice, resources, funny or serious quotes, identifiers) in sigs.
I can agree with this. I think most people motivated enough to start their own service will be able to make an insightful post. Along with that, making dumb posts hurts your image and by extension the image of your company, which promotes good posts.
I would agree if it wasn't about your signature.
It's not about my signature. I've had that since long before every other user had an ad in their sig.