SEO is the new spam. We solved spam pretty well, but it was a very different solution space to what is available for the web: - Spammers had basically two ways

SEO is the new spam. We solved spam pretty well, but it was a very different solution space to what is available for the web: - Spammers had basically two ways to verify their efficacy – they could either sign up to every provider under the stars and test each email with each of them individually, or they could use the absence of a signal as "proof" of being caught by a filter. But neither of these are very efficient. An SEO expert can simply wait for the search engine to detect their changes and verify the result with two or three search engines quickly and automatically. - For practical purposes whether an email is spam is answered in a binary form: either it ends up in your spam box or it does not. Removing spam-looking things from search results entirely would be devastating for any site victim of a false positive. And how do you implement the equivalent of a spam box in a search engine in a useable way? - Spam filtering was implemented in different ways on every mail provider, so the bar to entry was "randomized" and spammers would have to be quite careful to pass the filters on a large subset of providers. ISPs and users currently have nowhere near the resources to implement their own ranking rules, but maybe this could be a solution in the mid to long term with massively cheaper hardware.