I have come to believe that businesses should not be legally allowed to store any consumer data unless it's obvious to the consumer that it's absolutely required for the primary function of the service, and they should only be allowed to store data for that one function, with an exception if the consumer explicitly and voluntarily opts-in for each additional function.
Large internet companies have been collecting swathes of data with the claim that they are secretly using it to improve people's lives. But it seems to me that A/B testing has failed to improve anyone's life.
Example: I use search engines to search for something I'm looking for.
I do not benefit from being shown 'targeted' ads, nor from the search engine identifying the most populist answers which it uses to spoon-feed me later rather than serve what I asked for, nor from the search engine identifying which particular arrangement of pixels will leave me personally more addicted.
Businesses are welcome to use my data in ways which are in my interest, but they should not get to decide which of these uses are in my interest.