Old school webmasters (perhaps this is redundant phrasing) know that's okay. Back in the day, you'd say "I'll put your animated gif on my site for $500 per month" and if you had a networking forum Cisco or whoever would happily pay that secure in the knowledge that your viewers were in the market for their product.

Lesson: target the content, not the viewer. You know the general demographics of who is engaging positively with the tweet, and you show ads relevant to that group. A small fraction of the viewers need to be logged in for that to work.

Print magazines worked on the same principle; the ones that are left still do. I subscribe to one magazine. In it, all of the editorial content is up front and the back third is nothing but ads. I still read them -- sometimes I start there! -- because I genuinely want to know what's going on and what products are available in the niche this magazine covers.

This seems like so obvious an observation that I don’t get why advertisers haven’t made it. If I’m in work-mode, and you show me an ad related to a hobby of mine, I have a 0% chance of clicking it. If you show me an ad related to my work, it is probably more like .01%. Which is still an infinite-times improvement.

It's because there's an arms race to maximally exploit the massive amount of data they're collecting about individuals. The more specificity you can claim, the more the ad-buyers will pay. I'm not convinced it's doing any good, but I think a draw-down would be a hard sell for all parties involved in that market.

Re-targeting ads seem like a joke. Many times I've already bought their product or competitor's and am no longer interested. Hopefully they are paying for click throughs and not impressions.