Shinebox,
Okay, I thought about it some more and have concluded the revenue growth shown is indeed exponential. Yes, the revenue value of a series of points over equal periods is a constant multiple of the previous value. This is the case even when continuously compounded interest is used. A linear growth curve would not have each point being a multiple of the preceding point over a given period; rather, it would be a constant added to the preceding value. In our case, the revenue gained in each period is increasing considerably.
Again, I may be missing something, so please correct me if I'm wrong. Thanks again for your feedback.