Do billboards work?

Red Maxwell sends in this great photo. He reports that for the first week, all six muffins were in place.

My colleague Jay Levinson taught me that the two best words to have on a billboard are, "next exit." I have serious doubts that you can cost-effectively sell an item that isn't a "right now" purchase from a billboard, though. I'm have no doubts at all that hospitals have no business whatsoever running ads on billboards. "Oh, George, you've been thinking of having heart surgery--look at this great ad from Memorial Hospital!"

So, yes, it's funny and even memorable. But is it selling muffins or a particular brand of muffins? If I got a muffin craving from this ad, would I pay extra for these particular muffins?