could it be related to Norvig's law? "Any technology that surpasses 50% penetration will never double again (in any number of months)". A drop in growth could m

could it be related to Norvig's law? "Any technology that surpasses 50% penetration will never double again (in any number of months)". A drop in growth could mean that all the world became suddenly worried about privacy, sure. But it could also mean that Facebook is reaching the possible growth limit in certain countries.