I concur with this study
From experience in business and socially, I have found a direct correlation between the behavior of those who frequently use Facebook and/or Twitter. I do not count those who (like me) have created accounts simply to see what it was all about, but do not use the services on a daily, even weekly basis. Here are my (plain to see) observations:
1. Lacking in social skills that would be common prior to online communications
2. Exceptionally poor at returning communications of any sort
3. Socially short term. IE, will arrive for an event only to 'move on' later to another 'event' perhaps itself triggered by Facebook, Twitter etc.
4. Unfocused in their work, significantly reducing their productivity
5. Obsessed with their online status and number of friends or followers
6. Trying to impress 'someone'. Thing is, who?
7. Generally unskilled. None of the people I know who are excellent at something (music, coding, rowing, other aspects of life) have time to use such services that are a drain on personal productivity and the physical activities that are good for ones health and mental wellbeing.
The excuse that such services help people keep in touch is untrue. All those I knwo who are true friends go to the effort of exchanging new phone numbers and/or email addresses becuase they value their friendship to such a level they will make that effort.
Either way, while these services do have their pluses, they will not continue to grow once people realise their bodies have evolved to use all 5 senses.