About 12 years ago, the number of good blogs on every topic started growing fast. Soon there was too much good stuff to keep up with. It was overwhelming to find and follow all of the interesting people.

About five years ago, took off. A lot of people couldn't understand why became so popular so fast, but in hindsight the explanation is clear: Twitter enabled us to follow a large number of people without mental overload. The tweets go by. You take 'em or leave 'em.

If you have the time and mental bandwidth to follow, say, 20 good blogs, you might instead follow 50 with RSS or 1,000 via Twitter.

If you understand each new evolutionary step in social media -- blogs to RSS to Twitter -- as opportunities to increase the number of posts we can handle, then you'll also understand why pictures are the necessary next step in that evolution.

It's a response to social networking fatigue syndrome. We evolved from reading a small number of blogs and posts to reading a very large number of short posts (Twitter) to now just browsing content by getting "impressions" from pictures.