Indeed, this is one major problem in the SEO industry. The lack of certification or standardization leaves the door open to many less than competent people.
In my opinion, what makes one person a SEO professional is anybody who:
_ has extensive knowledge about SEO.
_ is up to date on the latest SEO changes.
_ is capable of doing SEO for himself.
_ is capable of teaching SEO.
_ has a proven track record of successful SEO work.
_ understands SEO and is capable of making sounds decision and providing useful advices not just because of what he or she heard, but based on facts and personal researches and observations.
There may be other important points, but those are the first that come to my mind.