You guys see this from shoe? List of networks and product owners who don't pay their bills http://www.shoemoney.com/deadbeats/
Yep. I also have seen it. However, that is a dangerous game. Other forums have tried similar in the past, and taken it down once the lawsuits and C&D's began. He's not the first to think of this concept. Many others have tried, and folded in short order. Unless you have well documented proof, both Shoebitch and yourself, are open to a lawsuit.
Yeah this is tricky... because I personally know one advertiser on there that hasn't paid because of bad traffic. They do pay fine when the traffic is legit, so it's a slippery slope. The Facebook group is a little better, because at least it gives the advertiser a chance to respond.
