An apt, 10,000 foot level view of the evolution of Twitter from Mr. Cody Brown (emphasis his):
Twitter became popular before it had a mission. What this means is that its employees and investors will forever be trapped in boardrooms having these inane cyclical discussions about its identity. Twitter will either perpetually be simple insofar as its millions of users will have to hack the service to reflect their own values or it will roll the dice on a focus, put the site through chronic redesigns, and risk a mass user exodus. Either way its top talent will likely get frustrated and leave the company. Its top users will drift to something else then jump.
I generally try not to get sucked into the discussion about Twitter, its values, what it’s useful for, etc. and Cody finally articulated why: it’s a tool with unique characteristics that has been bootstrapped into many different uses. Those that I can identify are ease of use over SMS, 140 character limitation for messages, asynchronous user relationships, and “push”-esque notification system. It’s just a matter of time before other tools appear with potentially the same characteristics but are designed to solve the communication needs of a better defined community.