July 17, 2009, Marco Arment:

I’ve never doubted the viability of running a serious business of writing iPhone apps before. For the first time, now, I am.

September 23, 2010, New York Times’ Bits:

On Tuesday Marco Arment, the chief technology officer at the social networking site Tumblr, announced that he would be leaving it to tend to a personal project: Instapaper.
[...]
“Basically the plan is to keep doing what I have been doing with it,” he said, adding that it’s always been a profitable business. “Now, there are features I want to create and business relationships that I’d love to explore.”

As an avid user of Instapaper, I’m so glad that Marco made it a profitable business after all.