So by your logic, I assume you don't use a credit card or check card. You pay full price for things at the grocery store vice using the store discount card. You don't have a cell phone, or cable/satellite tv or ISP? You don't do online banking? Drivers license, taxes, airline tickets, bills, you give away so much information for free, might as well get paid a bit.
If you spend your time worrying about stuff like that, that means you have something to worry about. Its pretty easy, don't cheat on your spouse, don't lie on applications or to your doctor. As for the junk food thing, they would have to oust the 80% of our nation that is obese. Mexicans will have taken over by then, so no worries.
As for the surveys, they never ask for your name or address or phone number and so on. All they ask is your birth year, sometimes date, but I give em the wrong date, right year, sex, and skin color. If they ever ask for more, which I can't remember any of them doing, then I don't participate. The scanner one does know my shopping habits, but buying various items does not mean I eat them? I can buy a gun tomorrow, doesn't mean I am going to shoot someone with it. That is 100% circumstantial, the fact that a lawyer gets away with **** like that is another problem in our country...a bit off topic.
By the way, I just pulled up your profile, now I have your email, your city, how many posts, when you were logged in....j/k, well, I can get those things, but you get the point. You cannot be secure in today's world. Its like social security numbers, the military uses it for EVERYTHING!!! Now they are heading to last 4 only, but we have schedules posted, now I know when I everyone has duty, when they are going to appointments and so on... there is no such thing as privacy. I also think of internet passwords, the longer they become, the better the program that hacks them becomes.