Currently, over 90 percent of people in the U.S. have mobile phones and estimates of smartphone users generally run between 70 and 80 million people in the U.S. It's even more important if you're trying to reach those oh-so-valuable 18 to 34 year olds: 42 percent of smartphone owners fit this age bracket. Looking at it another way, fully 62 percent of mobile users aged 25 to 34 own a smartphone. And, as I reported in my last column, 40 percent of smartphone and tablet users break them out when they're watching TV.