John Borthwick on the development of the iPad app, including the the “see what your friends are reading, too” feature:

For the first version we wanted to simply take your Twitter stream, filter it using a bitly-based algorithm (bit-rank) and present it as an iPad app. The goal was to make an easy to browse, beautiful reading experience. Within weeks we had a first version working. As we sat around the table reviewing it, we started passing our iPads around saying “let me look at your stream.” And that’s how it really started. We stumbled into a new way of reading Twitter and consuming news — the reverse follow graph wherein I get to read not only what you share, but what you read as well. I get to read looking over other people’s shoulders.

The Background of the iPad App