I really wonder this. I never clicked a signature ad and am wondering if it works for gambling sites. I need to be enlightened in this topic, because it looks like a waste of money to me.
Obviously if you're not a type of a guy who likes to gamble there's no reason for you to check out the signature link. It's not a waste of money to run a signature campaign, once you create a campaign and target a certain area for your product to be seen by the members. Guaranteed they will click the bait.
That is why we can see different types of advertisements in the signatures, and the reason is clear, because every company/website wants to attract particular target of customers.
It is only up to us, what kind of services do we exactly need from the bitcoin related projects.
However we should never tolerate any kind of aressive campainings where the signatures literally spam the big part of the forum interface.
Also, we should not see any obvious scam in someones signature, but im afraid we cannot do anything about it, except reporting the user.