Social media usage—both for personal and business use—is so widespread that occasional social implosions are relatively commonplace. How widespread? eMarketer estimates that roughly nine out of 10 companies use social networks as a marketing tool, and that level of involvement has been steady for years.

As digital natives who mostly lack smartphones, kids have a distinctive pattern of digital usage—lots of digital video, little social networking, worrisome amounts of screen time and so on.

In the latest episode of "Behind the Numbers," eMarketer's Mark Dolliver discusses how teens indulge in too much screen time, and the extent to which they and their parents see this excessive usage as a problem.

Younger baby boomers are not a digitally clueless bunch, but marketers cannot assume that they are as digitally active—or as mobile in their usage—as millennials and Gen Xers. Rather, they have their own distinctive ups and downs with digital.

Daily time spent with digital media will surpass traditional media in 2018. Increased time with digital video, which will reach 1 hour, 26 minutes, is a main driver of the increase of time spent with digital media.