I think I remember that SCID test...that was probably the one our psych-major sister gave us and all of us, including the girl who never had more than one beer, were alcoholics.
College drinking is not regular drinking. Period. 99.9 of the people I knew in college who drank like fish are now leading perfectly normal lives.
I also think the binge drinking definitions are bull, because everyone's tolerance is so different. I really dislike the use of these terms, because they often become self-fulfilling prophecies.
If your friend is blacking out regularly, missing work/school because of drinking, or having problems with friends because of it, there's a problem. If they are simply having a couple beers every night to unwind, and never getting drunk, I don't think you should worry.