Why is Twitter growing so rapidly?

Twitter by definition is a micro-blogging service that allows people to type in short messages or status updates that can be read by people following them. An individual message or status update is often referred to as a 'tweet'. Find out more about Twitter.
webtrends.about.com/od/web20/a/web20-glossary_2.htm

According to Websters Dictionary, Twitter is to utter a succession of light chirping or tremulous sounds; to tremble with nervous agitation or excitement; light tremulous speech or laugh. 

I personally do not have a Twitter but how I would operationalize this in a research paper I would create my own personal Twitter account.  This way I can live the life of a "Twitter er" and maybe fully understand the addiction that it produces.  I would take notes about the things I thought were important to Twitter about and even scope out other users and their twits to see what they believe is important.  Interviews with Twitter account holders could be arranged and questions such as 'Why is Twitter important; How often does one use Twitter; What do users really think about the 140 word limit; how long has the individual been a member,' could be asked.