Nifft, I hope that doesn't apply to any ads I might have in my sig. I certainly don't mean to offend. I only put up ads for E.N. Publishing's products, and that's mostly because Russ needs to save ad banner impressions for other people to buy. To put our own ads in the top-page banners would be competing with ourselves.
As a browser of the boards, and as a person financially affiliated with EN World, I'll say that I don't mind people with product ads in their sigs, as long as they're not just spamming advertisements. If a bit of free advertising in their sigs helps them be successful, it improves the chances of them being able to afford a banner ad, and it makes them feel that EN World is of more value to them.