I too am not a contributor, but from studying arabic (mainly on arabicpod.net) I can say that MSA is supposed to be the common arabic that is understood by all arab speakers. MSA is, I understand, used in current formal and semi-formal settings and newspapers. It differs substantially from Qoranic arabic which is more formal and uses archaic, and it differs from the arabic standard colloquial and the more "national" colloquial forms of the regions of the arabic countries. Interestingly, unlike colloquial in say English, the writing of the arabic colloquial will often follow the way it is spoken. I understand that if you were to use MSA with native speaker, the speaker will understand you but will instantly suspect that you are foreign because native speakers use colloquial forms in one-to-one communications. MSA is just too formal ("high" sounding) for the individual conversations.