There's a great site where some clever people have been analysing tweets you can see how happy twitter users have been since 2008 till today(!). Below is the front page graph they have plotted, looks like in general the happiness has gradually decreased since 2008.
Whether we can/should use something such as tweets to analyse emotions in people I'm don't know. I am aware of studies in the past using tweets where the spread of illnesses has been tracked across the world – fascinating stuff. So let's not just assume twitter and social media is some shallow, unhelpful tool. Let's appreciate the good that it can do too, good that is far bigger than most of our expectations.
And let's not fall into the trap of suggesting that it is because of social media that happiness has dropped(!). I was once at a Christian Leadership Conference where one of the biggest 'amen!' vocal responses from the crowd over the whole weekend was when one person mentioned a negative aspect of social media. When so much quality stuff was shared at the weekend about our faith and leadership, I was a little gutted to hear everyone get excited over the one mention of the 'dark side' of social media.
Take a visit to www.hedonometer.org to find out more about this happiness scale from twitter. Any further thoughts greatly appreciated, some will love this kind of things! others not so much.