Do you really think it's how ad networks figure out someone's marketable interests? Based on their draft email/chat messages? You obviously haven't tried doing something like this, but getting solid inferences from such tangential data is very hard, and it's not really a priority when the same users leave such a large trail from their browsing and searching anyways, visiting countless websites with promiscuous audience reporting, ad tracking cookies, etc. Why would someone bother to track someone's draft emails to figure out their political affiliation when the media they consume provides all the signal.
