I might have considered it before I got my current BF. I could not get comfortable on a Brompton, at least not as the dealer was able to configure it. And I'm 5'4" so weight carrying the bike up steps at BART was a major concern. Maybe if I had the option of a 16" wheeled bike that was very light, that actually rode well and - most importantly - could be sized to fit me, I would have chosen it. The Backpack/folding business would have been a very low factor. Had I gotten one, I would have only folded using the rear triangle in most cases; breaking it down just seems unnecessary with a sub 20 pound weight which I can carry assembled and well balanced. Of course, now I can carry my 20" BF as I've developed a few muscles ;-).

I supposed it might make sense for folks with small studio apartments in NYC or SF because you could even store it under a bed. Otherwise....not so sure about the folding/backpack thing.