The reason for this is simple: it’s the primary method by which most gallery post sites acquire their traffic. It’s also a major component of the lack of trust that many surfers have towards adult sites – a lack of trust that manifests itself in the poor conversions that gallery post traffic typically results in.
Don’t get me wrong; the over-abundance of free porn available at these sites is the number one reason why this traffic is non-productive (“Why buy the cow when the milk is free?”), but the fact remains that if the surfer can’t trust you to send him where he expects to go, he’s not going to trust you – or anyone you’re associated with – with his credit card information.
Some sites skim more than others, often to the point where you can click a link a dozen times before hitting the gallery. Some, but very few, gallery posts don’t skim clicks at all. Savvy surfers pick up on this pretty quickly; bookmarking sites that don’t skim (or skim at low, predictable levels) and avoiding sites that skim at higher levels.
I’m not opposed to traffic trading, but many webmasters need to carefully re-think the way in which they trade this traffic. After all, if you were at the mall and about to walk into the food court to grab a bite to eat and someone grabbed you and pushed you into the shoe store, would you be likely to buy a new pair of shoes? Me neither.