We can expect to hear more about this in the future. The amount of data that these trackers are gathering goes way beyond simply tracking who goes where and watches what. It removes forum anonymity and indexes what people type on forums, private messages and anywhere on any site. This happens while people have no idea this is being done. Nor that data between sites can be combined in far reaching manners. The data is then resold to national and foreign commercial parties including insurance agencies, financial organizations, health organizations, etc, etc.
The data is being used to refuse services, contracts, jobs, insurance to people because what they privately type on websites puts them in a risk category.
Its really doubtful these practices are all legal.