You can tag anyone on Facebook even if they don't have an account. When you start typing their name a drop-down box of suggestions appears. Hit the escape key and you can continue typing their name and tag them.

Anyone with your photo can associate it with your name on Facebook even if you don't use it.

Ah just check and yes you are right, apologies. Do people actually do this? Pretty ignorant if they do!

Exactly. We cannot have any expectation of privacy in public and likewise, we cannot have any expectation of privacy in online social media.

There is a fine line between "somebody who knows me (even if not personally) can recognize me on the street" and "everybody can know everything I do out in public or online"