[eertami]

What are the downsides to using Facebook as a communication tool? I have: a fake email, a fake name, no mobile number attached and I don't post statuses.

Facebook groups and messages however are just so incredibly convenient and ubiquitous that you won't be able to convince entirely separate groups of people to leave and use a service you mandate - unless you are friends with solely technical people.

Could I be a member of the groups and organizations I am without being in the Facebook groups? Sure - but it would inconvenience everyone, if there's a discussion in a group, and someone tags me to get my opinion on something, I can fire back a reply. They don't have to call or email me separately.

[psykovsky]

So you think Facebook doesn't know who you really are? Just because you use a fake name and email and no phone number? That's cute...

[worklogin]

They know who you are. Rather, they know that someone exists with your cultural, political and social preferences, and with all the people with whom you're friends.

And then people tag you in their photos. So Facebook may not strictly know your name, but any agency (of course, never in America!) who backdoors or coerces Facebook could learn everything about you.