What's not in doubt is that it is the undisputed, preferred microblogging tool of public figures, companies and private individuals for posting short text messages online and sharing links.

It has even played an important and controversial part in political uprisings, in particular in countries with totalitarian regimes where pro-democracy activists have found Twitter to be an effective yet stealthy communications tool.

Although it caters to the consumer market, its microblogging concept has been adapted by a growing number of enterprise software vendors who now provide Twitter-like services for workplace collaboration and communication.

As it celebrates its fifth birthday, Twitter also finds itself without several of its most public representatives, including co-founders Biz Stone and Evan Williams, who have recently moved on to other ventures.