
If you make a web application or mobile platform, one of the trendiest things you can do is add APIs and a software marketplace to it so developers will extend your product. Google is previewing its application market for Android, T-Mobile USA has promised a new applications store for its phones, and many people believe Microsoft bought Danger in order to get its software store technology.
The idea of encouraging third party developers dates back at least to the early days of MS-DOS, but it was associated mostly with operating systems until Web 2.0 applications took off a few years ago. Google played a big role in that change, by exposing APIs to Google Maps that made it possible to embed maps in other web applications. That helped Google Maps quickly blow past established mapping services like Mapquest, while the installed base of Google Maps extensions made it hard for Microsoft’s Web mapping product to gain traction.
The drive for web APIs got another big boost when Facebook enabled developers to extend its functionality, driving an explosion of widgets for Facebook that helped it grow past MySpace to become the #1 social network in the US.