As I thought about this topic more, I couldn't get past the obvious -- the terms "amateur photographer" and "profressional photographer" are widely known and used, rightly or wrongly, suggesting that one can be a photographer even if they don't make their living doing it. Then I went to my Heritage Dictionary. A photographer was someone who takes photographs, especially as a profession. A professional was not only someone who was paid or made a living doing something, but also someone with great skill or experience in a field or activity. An amateur however, was defined as either an unskilled person, or as someone who did something without getting paid for it. [although the root of the word is from the Latin amare, to love, this did not actually appear as a definition].
So what does that tell me? I guess if you really wanted to, if you take a picture with a camera, you could, by definition, call yourself a photographer. You will probably offend some people who believe you should have some degree of skill, or passion, or experience, etc., but the American Heritate Dictionary would back you up, at least nominally. Most of use would agree that really you should have some degree of skill, or passion, etc. before calling yourself a photographer, out of respect for the photographers who have earned our admiration through hard work and vision. What exactly it is that allows one to call oneself a photographer, beyond dictionary definitions, makes for a good discussion, as we've seen here.
By the way, a dentist was defined simply as "a person whose profession is dentristy". Nice and simple, that one.