By now I think we all recognize that large free services on the internet exist to make your information - your buying habits, your interests, your searches, your quirks - marketable. You, in essence, are the product.
For me, the darker side of free on the web is that it takes advantage of the good will created by millions of people who offer bona fide free content without any expectation of return. Companies like Facebook have put down roots in a land tilled by people who are legitimately offering content and services and are now choking out the native dwellers.
It’s not only that these companies are quietly selling us, it’s that they’re cynically stealing the good will of free at the same time.