It depends on how much you trust the web service with your data and how much meta data they gather about you, and how much you care about that. It is not as si

It depends on how much you trust the web service with your data and how much meta data they gather about you, and how much you care about that. It is not as simple as you are making out because of 1. The vast amount of meta data that can be mined from your browser requests, scripts running on sites, your logging into multiple devices. 2. The scripts that run on other sites when you are not using FB, that know your FB identity or might send data back to FB. Safe to assume it's being shared with 3rd parties. Safe to assume those parties are in different countries with different laws. 3. The amount of computational power FB has, machine learning technology etc. 4. What we learned from Snowden. It is naive to think of giving information to Facebook as being the same as giving it to a small community site running PHPBB. There are personal privacy concerns, as well as aggregate ones. I.e. by being on facebook you are helping other's to have less privacy unless you use it in a very restricted way.