The Wireless City
This is true to a degree, as people typically spend more time on their cell phones when out in public than conversing with one another. But I doubt that mobile devices are totally to blame for this. We have whole generations that were raised not to talk to strangers, so there's a reluctance among many to strike up conversations with people we don't know.
Devices sometimes have the opposite effect, causing people to unintentionally intrude on others. Consider someone talking very loudly on a cell phone; it's hard for one to ignore what may well be an intimate conversation. In another time, that person could have gone into a phone booth and closed the door for some privacy. Now, there seems to be no concern that others will hear details of one's personal life. Once, I sat next to someone -- a manager of some kind -- discussing the specifics of having fired a subordinate!
Another widely publicized phenomenon has been that of people watching X-rated movies on DVD players in minivans and SUVs. As weird as this might seem, it's another form of intrusion. Ever pull up behind a minivan in traffic where the DVD player was clearly showing SpongeBob Squarepants? Imagine a family pulling up behind the same minivan and inadvertently seeing images of nudity or explicit sex...
Part of the problem is that we might need to re-learn how to use and behave in public spaces. This might sound strange, but many of us did not grow up with public spaces. We grew up in suburbs where public spaces were rare at best. Malls were an exception, but there, people were expected to shop and eat, not socialize. Cities had more public places, but many of these were unsafe and best avoided.
Source: Future Now