There are no annoying Mafia Wars notifications here, no targeted ads, no anxiety-producing friend requests -- nothing but real-time messages from whomever you're interested in, be they Lady Gaga or the girl next door.  On the other hand, all is not well in Status City. This week's cover story in Fortune warns that Twitter usage appears to be flatlining.  One hundred million of those citizens are absent altogether, and Twitter.com has fewer visitors per month -- about 20 million -- than MySpace, according to comScore.  The company has a steady hand on the tiller in new CEO Dick Costolo but lacks a visionary product leader (Dorsey is equally focused on his next company, Square). It still suffers from irritating outages and isn't turning a profit.  And as CNN reported on Wednesday, UberMedia, the company behind mobile Twitter apps like Echofon, is planning to build a rival microblogging network, one that may shun the famous 140-character limit.  So are the buzzards circling over Status City? Should tweeters head for the hills or prepare to move to a competing town with fewer regulations?  In a word: no. The city that Jack built is a lot more robust -- and unrepeatable -- than it may seem.  First of all, let's look at those numbers. They vary wildly according to which service you use and how you slice them.  Quantcast says there has been a 50% jump in Twitter usage in the past five months. Most of that is overseas: Google Analytics says international traffic has risen 83% in the past year.  And because so many people are tweeting on their mobile device or third party app, the Twitter.com numbers are incomplete and misleading.
In the beginning was a word, sketched on a legal pad. And the word was Status.That was the working title used by programmer Jack Dorsey in 2000, when he designed the service that was to become