This article has the best, simplest explanation of the internet I’ve ever read. Quoting a Metafilter thread, it says:
If you’re not paying for it, you’re not the customer; you’re the product being sold.
That’s all the internet comes down to. A profitable internet business is either selling a good or service to customers – or it’s selling the eyeballs it gets to advertisers. I can’t think of any other model.
So if you’re using a product that you’re not paying for, understand that you are the product, and the more data they have on you the more profitable a product you are.
It’s not the devil’s work; it’s just business.