use it in the same way you get those very loud, boisterous people use pubs and bars.
It's a way of airing their conversations to the public so that everyone else knows exactly what's going on in their lives.
It's also no doubt been responsible for a rise in digital camera sales. There's an increasing reliance upon cameras during nights out, and Facebook is solely to blame. It introduces a "let's take photographs of ourselves tonight, just to show everyone else how much fun we have".
Photography isn't as much about capturing moments for personal reflection and sentimentality now, as advertising your crazy lifestyle.