Currently, they have none. They have lots of expenses though. One of the biggest is the SMS fees... they pay for receiving and sending them. I heard an interview with Evan in which he said that the fees are in 5 figures per month!<p>How would they make money in the long run? Sell pro tools and statistics... similar to the way Feedburner makes money. Just study Feedburner and you'll see plenty of parallels.
<a href="http://evhead.com/2006/10/birth-of-obvious-corp_25.asp" rel="nofollow">http://evhead.com/2006/10/birth-of-obvious-corp_25.asp</a><p>Until today it's funded by Evan Williams who bought Twitter and Odeo from it's previous investor last year.
The more important question is, What in the Jumping Jack Flash <i>IS</i> Twitter. I have been to the site twice, heard people ooh and aah over it, and for the life of me I have no idea what it is. Dot com bubble anybody?
PG talks a lot about this kind of thing in his essays (and book). (Zemaj's answer is pretty good, too.)<p>There are two models I can imagine for Twitter: 1) working in advertising, or 2) become a feature of some larger business.<p>You might also speculate that there would be some permutation of Twitter that would be interesting enough to become Twitter Pro or somesuch. But those kind of things are not often very exciting.