One of the most dangerous trends in tech, both in terms of data security and human rights, is expanding monopolies of power by a handful of companies. We are increasingly trusting 3 or 4 websites with massive amounts of PII. Indeed, for many less tech-savvy folks, "the internet" is just 3 or four websites.
Facebook and Google operate in direct opposition to the Unix philosophy; "Write programs that do one thing and do it well"
Facebook, with a single ecosystem of development and propietary code, provides:
A social networking site
An instant messaging client
A payment processor
A second messaging service