I filled one out a few weeks ago, think it was still optional. I just put linkedin

... though having said that I have a very google-able name so if someone wants to find my facebook profile it's not very difficult

I put my Linkedin and my Twitter, don't bother with politicking on my Twitter and my LinkedIn is a hollow sad looking profile. Didn't realise it was optional and just put it in.

Can't wait to get turned away at the border when flying there in a few months for a new job for liking something years ago.

Last time I filled it out it was optional. Nor sure if that changed in the last year.

Yes, but it's optional