I'd say I am the exact opposite. I ignore 99% of advertisements I come across in signatures on forums that I am on. The only ones that I don't ignore are the signatures of people that I am buddies with.
I think a good way to profit from a site might be via VIP sections. It seems ads are pushy and ignored
ON another site I have like 18,000 posts and each has my banner in my sig. Does it help? well I had like under 10 clicks if I was lucky.
Yet again another website can be different. On another way less content yet more little traffic with two sign ups. It can go up and down and left to right
On 2nd thought, ads do make money - or people wouldn't be obsessed with them. In that case, it depends on how well you target things.