We're looking at offering a free banner exchange program to our cusotmers. It would be a 1:2 exchange (for every 2 impressions you get 1 impression in network). Now, what are the chances that this type of system would actually hurt a site rather than help it? Would SE's see this as spam?
As an aside, this is not an in-house project. We'd be partnering with a different company and they would provide the banner serving and coding.