You are an informed ad buyer, and you have appropriately gauged the risks. IMO, most people who buy ads are not informed. As a software engineer, I am concerned with the ability to build scalable, reliable systems, for which something can be reasonably said about their integrity -- their ability to resist being compromised or manipulated. IMO, the inherent anonymous nature of web usage, combined with the current limitations of Internet security and some aspects of its architecture, make CPC advertising a poor model. At the very least, I would like for any ad buyer to plainly understand these risks and limitations. If they wish to continue to buy, and make money off of the medium anyway, more power to them.