alt Hacker NewsWell, if you presented them with list of 100 partners each with 20 page of privacy policies and they accept it within 10 seconds it should be tricky to argue that user actually read it all.
You could, for example, require that user answers very specific questions regarding 10 randomly selected partners and how exactly they can use the data ("is partner x allowed to build very detailed profile of you and target you with political adverts that are designed to manipulate you?").
If you did this people would only use the same half dozen sites and competitors would emerge.
We're borderline already there today when the cost of switching is typing a different url at the top of the screen. You add some mandatory 20 minute wait and you'll never see a new site again.
Google and Facebook would love it though.