Negativity in blogs

In his article "The Revolution Will Not Be Blogged", George Packer notes that "bloggers are almost unfailingly contemptuous toward everyone except one another".

I have noticed that blogs (including this one) tend to be negative, snarky, cynical, accusatory, etc. I wonder if that's because anger and unhappiness provide the energy and motivation to write something—write a complaint, write a lament—to relieve our tension; whereas joy and happiness leave us relaxed and blissfully mute.