Lately, NTT DoCoMo hasn't had to push its customers to LTE so much as give them a gentle nudge. Just half a year after it notched up 4 million customers on its Xi service, the Japanese carrier has already reached 10 million -- no mean feat when it took the carrier a year following the 2010 launch to get its first million. Of course, it's not too difficult to explain just why adoption has been accelerating. Along with expanding coverage and improved speeds, DoCoMo has been releasing LTE phones aplenty to virtually guarantee that customers will move to 4G. Still, we don't see any sign that the trend will stop when the carrier is launching a slew of high-end devices to catch 3G stragglers.