Just been trying to sign up to SS and they are asking for a scan of passport or similar ID (wish they'd ask at the beginning and not end of registration) - I've not been asked by any other sites for this.  What is this all about and is it legit?

i believe this helps them stop people from signing up as their own referral, signing up as a buyer and buying their own pics, and let's them know which country you are legally from for tax info.