It all boils down to not giving anyone information that could put you in danger.
Nothing bad in an old fashioned face to face meeting at a public coffee shop where you can talk face to face (normal conversations) and get a gut feeling of the other person.
Need an id photo so you can recognize for the meeting? give one that is already on the net, and literally anyone could have grabbed from Google. It is you in the photo, but no proof you were the user sending it.
Now, if you start sending images of yourself doing ilegal things to prove you are legit, yes. You *will* most likely be blackmailed sooner or later.