PC's are modular. You can mix and match (at least, until a new motherboard standard); you can replace parts (at least, while they're still made). One problem w

PC's are modular. You can mix and match (at least, until a new motherboard standard); you can replace parts (at least, while they're still made). One problem with mobile phones is that they haven't been fast enough - by tightly integrating every part, you can maximize efficiency to get the best out of the hardware. Apple does this fantastically, whereas Android is more modular, and so isn't quite as efficient. But now that the iPhone 5S is 40x-56x faster than the first iPhone, speed doesn't seem to be an issue, in practice or theory. So an even more modular phone is plausible.