"I think that we need to hold the web sites accountable for the content that they display. If browsers get infected by ads at Forbes or people buy knock-off watches from ads at Yahoo, then we need people to sue Forbes and Yahoo. Remember: these web sites authorized the placement of the ad on their web page."
So effectively what you're saying is that we should eliminate ad networks. There is no reasonable way to screen every ad before it is shown when using an ad network. So in order to be safe from lawsuits, publishers would have to go back to directly contracting with advertisers for every ad. Certainly there would be some benefits to that in terms of reduced low quality ads. The problem is, the added overhead of doing so would put many small publishers out of business. Dealing with individual advertisers is a huge job, with massive economies of scale; it just doesn't make sense for websites that are orders of magnitude smaller than Forbes and Yahoo.
So effectively what you're saying is that we should eliminate ad networks. There is no reasonable way to screen every ad before it is shown when using an ad network. So in order to be safe from lawsuits, publishers would have to go back to directly contracting with advertisers for every ad. Certainly there would be some benefits to that in terms of reduced low quality ads. The problem is, the added overhead of doing so would put many small publishers out of business. Dealing with individual advertisers is a huge job, with massive economies of scale; it just doesn't make sense for websites that are orders of magnitude smaller than Forbes and Yahoo.