Two words: Time. Sink.
This is probably the next evolution of that phase when everyone hit F5 incessantly, waiting for the next email to drop into their inbox. Instant messaging and social networks are prime culprits for instant notifications, and even if you do not realise it –kill your time silently– because you spend so much time waiting for something to happen. A possible chat, a reply to a comment, something – anything!
To be honest, it would be just the same if we checked our notifications three times a day, rather than have that tab open all day long waiting for –you know the drill– something to happen. So much time could be used for something else more constructive than staring at your browser.
So get off your Facebook, Twitter or IM, and get started on something that’s been lying on your to do list for ages. You might just be surprised how productive you could get.