Twitter Turns Five as Site Registers 200Million Users

'Inviting coworkers'. Two words. Not spectacular. Yet, as the first ever Twitter message – made five years ago today – those two words sparked a revolution in internet communication. It took three years to pass the billion-tweet mark. Now it posts that many every week.Since co-founder Jack Dorsey posted it on March 21, 2006, Twitter has registered nearly 200million users. Dorsey has spent the