parasite, noun 1. an organism that lives on or in an organism of another species, known as the host, from the body of which it obtains nutriment. 2. a person who receives support, advantage, or the like, from another or others without giving any useful or proper return, as one who lives on the hospitality of others. 3. (in ancient Greece) a person who received free meals in return for amusing or impudent conversation, flattering remarks, etc.
Facebook, Google, and all the free services operate as parasites. So do the "discount with card" groceries, etc., etc. All of these operations are pushing you to give them your information, which they will use to manipulate you. And when they’re done manipulating you, they’ll sell your information to others, so they can do the same.
Regardless of how creatively this is justified, it is plainly parasitic.
It is true that when it comes to these kinds of "free services," the user is the product, not the customer. The customers are the advertisers, etc. who get your information or the use of it.
But that doesn't make the user/provider relationship "parasitic."
First of all, Google and Facebook don't swim up under your arm and attach themselves without your knowledge or permission. If you have a Google or Facebook account, you have one because you decided to get one and took steps to make that happen.
Secondly, what's taking place is an exchange of value. The user values Google's GMail or Hangouts or Voice or whatever service because he or she can use them to do stuff. Google values the user's information because it can use that information to sell ads to people who want to sell stuff to the user. Ditto Facebook's social media outlet, Messenger service, etc.
You may or may not like the product. You may or may not like the price. You may consider the deal too creepy for you, or just not sweet enough to be attractive. But "parasitic?" No. At least not any more so than buying a burger or a pair of shoes, or taking part in a focus group in exchange for cash or samples.
I know people who avoid Facebook and/or Google and/or some other such companies for various reasons, including not wanting their personal information floating around being used by God only knows who. And that's fine. It's even fine to try to convince me to do likewise. But if the best argument you've got is the absurd claim that the relationship is "parasitic," try again.