[matwood]

but it's become so ubiquitous that having a Facebook profile has become necessary to participate fully in online life.

I must not be participating fully in an 'online life' then. When I look at my non-tech friends I do much more participating online than any of them do and they all have FB accounts and I do not.

[sp332]

You can't even sign in to some websites without a FB or Twitter login.

[adambyrtek]

Blame those sites for that, there is no excuse for not offering alternative login options.