Using an alias is NOT the same as using someone else's identity, be it their name or photos. On the one social media platform I use, to share photos with friends and family, I use an anagram of my real name. Also, I'm not sure how AM works, but for practically every other website out there, when you use an email address, you get a confirmation email before your account is activated so I doubt there are many, if any, people who are on there because someone else used their email address.