For years and in college I was taught the definition of a "pro photographer" was when one starts to get paid for shooting photos. Perhaps in some ways this could be considered true. However, when a photographer claims to be a "Pro", that photographer is communicating that he can be trusted to shoot the same quality work he presents in his portfolio or website!!! The photographer that can do this 99% of the time is a true "PRO PHOTOGRAPHER" and is qualified to claim so.
The problem is this, I and many true pro photographers I know through the years and especially these days are having to come behind these "wanna be pros" and clean up their messes. It damages the reputation of our industry and people begin to think "well hell, I can just do this myself if this is what pro work is"!
Personally, I would like to see the photography industry adopt the same system plumbers use. If you are serious about becoming a professional photographer, but have not established you skill set consistently, then you need to call your self an Apprentice Photographer. Once you have establishes your skill set to be able to consistently deliver the same work quality in your portfolio and on your website and say have done so successfully for multiple clients over year or two's time, then you should call yourself a "Pro Photographer". Before that day, do yourself and the industry a favor and let your clients know you are still establishing your skill set as a photographer.
Just my two cents worth. Let me know what you think!