Seems like a person could create an unbelieving cheap podcast hosting business (Simplecast, Transistor.fm, etc) on the back of R2. For those unaware, the primary infrastructure cost of these businesses is serving up mp3. Much like what YouTube does for video.
Using B2 and CF workers to keep costs low currently but if R2 is as good as it sounds I have no reason to write any overages billing code. Lovely!