A serious Internet marketer wouldn't bother with that. Most forum signatures are no-follow. Forums aren't for advertising, SEO and all that. Certainly if you make a good contribution to a forum, people might take an interest in your signature, but it's not going to make you a living or get you a lot of exposure. It seems like 99+% of marketing/SEO advice out there is sleazy, dodgy nonsense, so be very careful what you take to heart.