One thing I wasn't completely sure about reading this was whether there was a service behind the app as well (other than the RSS feeds provided by multiple sites not by the author). I'll just note that anything he says here is undoubtedly even worse for apps that are buy-once but which have servers behind the scenes.

I'm sure that's another reason for the recent uptick in in-app purchases (beyond the profitability of in-game swag). I suspect that serving that market is also what's going to really drive (eventual) uptake of the Dropbox Datastore API assuming that data stored there is charged against the user's account(s) instead of that of the developer. Anything that may let you offload the costs of running a backend server - particularly onto a service that the end-user already uses and perhaps already pays for - is going to have a huge impact on your bottom line long-term.