Horace Dediu finds that the rate at which Americans are buying their first smartphone isn't slowing down. That's interesting, as for a while now we've already been in the situation where "everyone" has a smartphone so you might think the remaining holdouts are die-hard dumbphone fans or just totally cut off from the world of mobile. But that doesn't seem to be the case, and as he says it seems reasonably likely that vendors will stop making dumbphones altogether.
The engine of this supergrowth is, essentially, Google unorthodox Android business plan. By creating a workable, freely licensed smartphone OS they've essentially created a world in which there's no reason not to make a phone a smartphone. If you want to save money on parts by not installing the hardware needed to run up-to-date Android that's fine, you just ship with some old edition of Android and try to free ride on the brand. Thanks to Moore's Law, using three year-old technology is bound to be very cheap and you can be off to the races.