How about verifying the ads that you allow that are scams
Cotosen.com is listed on my "wake up" sites that it is a scam site. And yet you allow this company to run on your platform and also highlight on the side panels as a ligitimate business. Which then means you are complicit in promoting their fraud as you have other companies that you promote on your web pages. If you don't verify them, then I believe it is your obligation to let all your users know that you are not backing these ads with a money-back guarantee!
Timothy Hess commented
Just one of the ones that have been scams is "Cotosen" (cotosen.com). I ordered two of the products listed on Yahoo's advertising side of the page. Their site indicated normal shipping within 7 days. The company indicated that the material hadn't come in yet. I told them I wanted a date when I would receive the package and if I didn't receive the information by today Feb 11th, I wanted the order cancelled and my money refunded. I sent a email to them this morning indicating that the order was cancelled....refund my money. I haven't heard from them since Feb 4th.