What’s interesting to me from the above chart is the orange line, which represents Instapaper app updates. While the blue line shows a steep and steady decline of growth in app downloads, the orange line shows the size of Instapaper’s install base, which is significant. Unfortunately, there’s no great path to a paid upgrade if an app developer launches an update with a bunch of great features.
The only options for monetizing an existing install base are advertising (i.e. Facebook), creating a “new” app and converting your existing install base to purchase the “new” app (i.e. Tweetbot), or offering some type of subscription or consumable via in-app purchase (i.e. Evernote).
In-app purchases can be great for customers and developers. I still despise the way a lot of games do it, though.