Yes! Do this! I mean, if he wants to that is, but he does, I know this. LINUS, DO THIS FOR US <3
For me, the best part of the M8 is the fact that HTC just disregard the status quo for most phone manufacturers, with huge screens and ridiculous pixel counts on the cameras, and focus on what really matters, the UX. The One phones are built to a ridiculous quality level, and as you quite rightly said, for the majority of people they're not going to be printing out their phone pictures (I don't even own a printer anymore), they're just going straight to facebook or instagram, 4mpx is definitely a sweet spot in terms of getting a decent image without wasting space.