From the beginning, Twitter has asked its users one simple question: "What are you doing?" The original idea assumed the network would be a place for people to keep in touch with each other and the occurrences in their day-to-day lives.

But, as co-founder Biz Stone acknowledges in a Twitter Blog post today, that question has taken a backseat to a more important question.

According to Stone:

The fundamentally open model of Twitter created a new kind of information network and it has long outgrown the concept of personal status updates. Twitter helps you share and discover what's happening now among all the things, people, and events you care about. "What are you doing?" isn't the right question anymore—starting today, we've shortened it by two characters. Twitter now asks, "What's happening?"

Basically, Twitter realized that users don't checks the site daily simply to read about Joe Schmo drinking coffee at a cafe in San Francisco. The social search site has morphed into something more interesting, a real-time stream of the most important events occurring all around the world: users are sharing technological breakthroughs, discussing election protests, warning others about major traffic accidents, etc.

Though the update appears relatively small, it may signal a move by Twitter towards specialization. As a startup, it may never quite have known what the service would become fully, so it meandered somewhere between a social network for friends and family and a global network of tweets about global events. Now, it appears, Twitter may be choosing to embrace the second of those two a bit more, since that is why most people use the site.

If so, such a move should stifle the comparisons to Facebook a little, as no longer would Twitter be competing to be that kind of all-encompassing network, but instead just a real-time social search engine.