Released yesterday, Instapaper’s Full API for developers permits access to users’ libraries for use in new applications. Marco Arment goes through the thought process for how he plans on monetizing this new initiative (since the majority of his income is derived from the purchases of the Instapaper app).
It’s an ambitious business plan, and instead of complicating things (or screwing himself over by cutting off his primary revenue source), he’s made it easy. Any developer can use the Full API, but Instapaper users must subscribe to Instapaper ($1/month) in order to use additional apps with the API.
Nice direction, though I’m still more interested in seeing where version 3.0 is headed.