Just a few short years ago, it was surprising to learn that someone didn't have a landline phone. The "mobile-only" early adopters were objects of wonder: what if your battery dies? What if you experience a network outage? What if you lose it? It seems silly now. Roughly half my friends and acquaintances are mobile-only and I must admit that I dust my landline handset more often than I use it. Which brings me to a startling new statistic: a recent study from comScore found that 18....