[Fango]

Actually, it's a whole lot simpler than that:

Pros= Models who do it for a living
Ams= Everybody else, especially "real girls", from places like Webshots and elsewhere. Everybody else can even include girls who "get paid" as a one time thing.

Remember, we're dealing with connotations here, not denotations. "Amateurs" is just a catch-all term for anyone who isn't a pro.

Fango