ComScore released its annual US Digital Future in Focus report this week, offering a year-end wrap of many of the trends its tracked throughout the past year and a look towards the next. One of the more telling stats concerns email use among those in their teens and twenties. According to the report, web-based email use among 12-17 year olds dropped 31 percent in the past year, while use among those 18 to 24 saw an even bigger drop of 34 percent. Some of that can no doubt be attributed to Facebook and other email alternatives, but a big factor is the growth of email use on mobile devices; both of those age groups saw double-digit growth in that respect, with mobile email use jumping 32 percent among 18