How do you feel about the use of face recognition, Bluetooth, cell phone mac addresses, GPS (when you view an ad, so they can prevent fraud against advertisers) to track people who may be commercially relevant to customers of those companies? Companies aggregating that data. By looking at an ad, while using a cell phone, tablet or other device that includes built-in location tracking features, you often become trackable. If you take a picture, that picture likely includes meta data embedding the make and model and sometimes where it was taken.
For example, life and health insurance companies might be interested in how physically active people are so they could provide incentives to healthy customers and disincentives to unhealthy customers.
If they were not able to do that the cost for the average customer (who is defined in health insurance-speak as somebody in their 20s with no treatable health conditions, even if that is not in fact the average customer in society) to only rise a tiny bit even as the cost for sick customers may need to rise very substantially in order for the system to remain a profitable investment. If they were unable to channel those costs to the sick exclusively, the overall increase would crowd out more and more other spending all across society unless changes to a non-profit healthcare system like Canada's which are forbidden by trade commitments were made, at tremendous cost to the taxpayers in sanctions - such as what happened to the US when it lost the US-Gambling WTO case with Antigua-Barbuda,
conveniently establishing the legal precedent, except much larger, because the affected service sector would be a huge one. (Also it would require they change their entire philosophy, a change they would never be willing to make.)
Or where people go, that is information companies gladly pay for. Everything from the size and layout and location of the interior of peoples homes, to the places they spend their time, and who else is there, at the same time, it all might be helpful to marketing firms in estimating their income.
As was recently stated "what is good for the people is not necessarily what is good for Facebook".
For example, various promotions which (insert corporate name here)'s customers might run (the reasons the companies that sell them might pay FB for their data) would be wasted on the poor who would be unlikely to ever buy those products.
In general, I don't really mind this kind of "spying". After all, I have entered their premises voluntarily and I feel the business owner has a right to keep an eye on things. I don't care if they try to "profile" me either. It's not too different from what a human employee could do. I think the same applies when going out in any public place. For the most part, I think it is to be expected.
If this type of activity tries to cross the threshold of my home or is used on a personal computing device of mine, then it becomes an invasion of personal privacy and that's where I draw the line.
What if you gave them consent by clicking a yes button on a EULA when you signed up for some web site?