If you put the control in the hands of the people whose data is being handled, I'm sure a significant percentage will default to "Do not share" given an explici

If you put the control in the hands of the people whose data is being handled, I'm sure a significant percentage will default to "Do not share" given an explicit choice. People aren't going to directly assist and curate the ability for 3rd parties to spew more spam & spyware on their webpages and in their email inboxes. If they could see what sort of data is being tracked, that can easily trigger their creepiness receptors and wish to distance themselves from it. The only reason people endure the current situation is because they don't feel they can do anything about it, and really don't know the extent of what's going on. Empowering them will finally allow them to actively break out of that cycle.