I tried and failed three times before I began to understand the value of Twitter.  It is not solely to tell the world about the big chili dog you just ate or your mood although that certainly comes with it.  It is, with significant constraints in the form of 140 characters, a way to update various audiences about interesting things.

"Interesting things" are in the eye of the beholder but when I figured out I could use Twitter to provide not only a real-time update to this blog (see "Breaking" on the left panel) but use it to drive both blog and status updates to other applications (like Facebook) via either text message or web form that the light bulb began to go off. 

Also, Twitter's social features require minimal effort.  You can follow who you want, they can block you afterward but not deny you (there is an optional "accept" follow capability for those that want a bit of control) , you can see who others follow and they can see who you follow, you can direct message (an increasingly difficult message stream to manage) but can't forward, cc, or otherwise turn it into email.

Twitter gets grief from many directions about a business model and it is the right question to be asking.  The point to take away, however, is that roughly 3MM people have signed up for Twitter (via Wikipedia) with some subset actually being active users and building dependency on it.  It is a  way to directly engage with people all over the world in a forum different than a social site or as formal as email.  From a marketing point of view, it is an essential place to have a presence both to promote your news and products but to immediately respond to both negative and positive comments about your brand.  Both Dell and Comcast "get" this point and have a presence on Twitter with Dell claiming upwards of $1MM in revenue directly attributable to its Twitter presence and distribution of sales alerts.

It also forces a whole new level of focusing on saying things with brevity.  140 characters is not a lot of room to pontificate but the ability to embed hyperlinks via tinyurl.com provides even more flexibility.

How popular is Twitter?  Here's an article from the WSJ on it and here is one laying out enterprise use cases. Also, Guy Kawasaki weighs in on the marketing benefits of Twitter many of which I completely agree with.  Even members of the US Congress are using Twitter in an effort to drive transparency and direct communication.

No doubt, I am still learning and expanding my understanding.  I am tinkering with TwitterFox (a Firefox browser plug-in), Tweetdeck (a client application), and the various ways to search and tag Twitter content.  More to come…