"Would apps be able to sneak a look at your face and read your emotions?"
Years ago I went to a computer architecture conference where in a set of papers on power saving for PCs someone was proposing using feedback from the users responses to allow a PC to minimize power consumption by reducing clock speed until it detected the user was becoming unhappy with the performance. So, how long till we find Apple have added the "software update" that ensures old iPhones run just below the "happy with my phones performance" level to encourage the next upgrade :-)
Biting the hand that feeds IT
