  Virtually all of the rapidly increasing data traffic consumed by mobile users
requires some kind of processing, normally performed at cloud servers. A recent
thrust, {\em mobile edge computing}, moves such processing to servers {\em
within} the cellular mobile network. The large temporal and spatial variations
to which mobile data usage is subject could make the reduced latency that edge
clouds offer come at an unacceptable cost in redundant and underutilized
infrastructure. We present some first empirical results on this question, based
on large scale sampled crowd-sourced traces from several major cities spanning
multiple operators and identifying the applications in use. We find
opportunities to obtain both high server utilization and low application
latency, but the best approaches will depend on the individual network
operator's deployment strategy and geographic specifics of the cities we study.
