How does Facebook benefit with privacy leaks?

[NICKH]

A. they've been informed of what Facebook does with personal information.
Have you considering getting in the habit of reading the privacy policy for any website you give information to?
Whether or not this "steals" people's privacy when they've been informed is debatable.

Although, I think Facebook is an excellent networking site, they haven't made security and proper design the highest priority. In the beginning they were primarily focused on getting new features out which leads to a fix the broken stuff later mentality. A.

Facebook can target ads more specifically to the user then. Also, many websites sell this information in an aggregate sense. For other companies to know various online trends, can help them make their own marketing more effective, and in my opinion invasive. However, facebook and quality websites aren't free, so there's a tradeoff for the user between quality and privacy.