A Couple A Couple

We've covered the when-is-a-date-a-date issue, so the next logical step is ... when is a couple a couple? That is, when would you be considered "official" (i.e. boyfriend/girlfriend)? Obviously, there are some possible categories of "triggers": a certain level of commitment to the other person, a promise of some kind of exclusivity, and a certain amount of intimacy (mental, spiritual, and/or physical). But in your opinion, what defines those levels of commitment / exclusivity / intimacy, where that's when you decide you are official? (No. Don't jump to conclusions, people.)