The future of sustainable app development is to give away as much value as possible and empower those who receive more value to pay more for it.
He states later in his article:
I don’t think freemium makes sense for every app in every situation, but it’s time to get serious about finding ways to make it work for more than just games.
And he’s putting his money where his mouth is: his Timer app (which I use every time I grill) is now free.
I like how Seth Godin put it: Free ideas spread better than non-free ideas, and you monetize it by selling souvenirs.
That is effectively the business model I have here at shawnblanc.net. The site is free (with ads) to anyone and everyone, but for the “pro users” who want more, I have a daily podcast. And it’s the member support of those pro users that tipped the scales and made this site profitable enough that I over a year and a half ago I turned it into my full-time gig.