There's an old well-worn addage that says, "The customer is always right." On the surface, it means that you should always strive to provide good customer service. But on a deeper level, it means that if your customers do things with your service that you never intended, perhaps you should just go with it. That's likely what happened with Twitter, which started out as a place to report the random little happenings in your life, and has begun to evolve into a platform for serious discussion and breaking news.

When Twitter was first launched in July 2006 (as Twittr), it was described as "present tense blogging," a service "that helps groups of friends bounce random thoughts around with SMS." Even today on Twitter, the company's suggested use cases all revolve around mundane status updates. But somewhere along the way, Twitter was embraced by bloggers and citizen journalists, politicians and businesses, as a way to report, react to, and discuss news items.

We talked about why Twitter works so well for news in a piece here last month. We predicted that Twitter "will become an increasingly more important point for the distribution of breaking news during 2008, to the extent that traditional journalists will begin to pay more and more attention to it the way they have to blogs." It is perhaps Twitter's openness to letting customers define it that has led to its success.

I used to work in the computer game industry, which is known for letting customers define new use cases for their products. Computer game developers often provide tools for users to create modifications to their games that take them in new and unexplored directions. In recent years, many games have begun to be created with non-linear, open ended designs that let users progress through the game in ways that even the developers didn't intend.

"Computer gaming is supposedly all about interactivity, but typically we put players on rails and say, 'Okay, wiseguy, figure out what I want you to do here!'" said game designer Warren Spector in 2000. He succeeded in making his seminal shooter "Deus Ex" break out of that convention by creating a game that was so open ended that there were always multiple ways to achieve a level objective -- some that Spector himself never thought of until he saw players doing it.

In a way, computer game modifications are analogous to the mashup movement on the Internet. By providing users with open APIs, web app creators are letting their customers take their applications in directions that they likely didn't think of. It is not that developer should always listen to everything users demand of their apps -- you have to find the right customers -- but providing open access to your product's architecture and data and letting users remix it can yield mashups that turn your app into a killer app.

Google Maps, for example, is supremely useful on its own. But what truly makes it and other mapping services like it killer, is the ability for people to utilize and remix that data in third party products. Google's Maps API has been used in thousands of mashups, many of them are obvious, but I'm willing to bet when the company first started making the product they didn't think it would be used as the basis of a racing game or used to estimate cab fare.

And though there is certainly still a place for Twitter's original use case, and there are people who use the service that way, it is the ecosystem of corollary applications and users who have taken the service in completely unexpected directions that have made Twitter so special.

As a side note, interestingly, this article evolved in unexpected ways much like the services I was writing about. Its original title was "Getting Back to Twitter's Roots," and started out as a riff on the New York Times article I linked to in the last paragraph.