Ad tech companies are one virus in this nasty swamp.
Idiot marketing execs are worse. I occasionally speak to our marketing team monitoring our website and it is frightening how much granularity is available on who is viewing our site. I'm not sure precisely how it does it (no login functionality) but the marketing droids think it is perfectly normal to see user names, emails, company, location, company details for a moderate cross section of our users.
Granted this could just be those that filled in the "Contact Us / newsletter" details and based on ip address maybe?
Without this data the marketing droids will have less info and will panic (a very good thing IMO). They will likely try to migrate to whatever will make them look good in front of management ("marketing insights!" as they call it). A website marketer without any info is useless