Micro-blogging is a form of blogging that allows users to write brief text updates (usually less than 140 characters) and publish them, either to be viewed by anyone or by a restricted group which can be chosen by the user. These messages can be submitted by a variety of means, including text messaging, instant messaging, e-mail, MP3 or the Web. (from Wikipedia)
Micro-blogging is sometimes criticized for encouraging dull or meaningless posts, conveying the minutia of daily life, such as what the writer is eating, who the writer is waiting for, how far behind schedule the writer's flight is, and so on. This criticism, though, could be leveled at any communication tool, from longer-form blogging platforms to telephones to Post-It Notes. Not every bit of communication is riveting, but the potential for profundity and powerful prose is promising.
Additionally, the term micro-blogging, is perhaps more narrow than the true potential of the platform allows. For example, Twitter has often been compared to "time-shifted" instant messaging in which people can converse directly with quick messages without the need to be online together. Perhaps more common, Twitter can be compared with a chat room filled with only the people you choose to hear from, again without the need to be online at the same time -- although that's part of the fun.
Micro-blogging is what you make of it. The simplest way to think of the power of micro-blogging is to imagine tapping into the thoughts and lives of any number of people who have common interests, concerns, geography, hobbies or professions. You can:
Learn about new tools and ideas
Ask questions and receive immediate feedback, and
Develop a deeper understanding of the people with whom you connect online.
Pros
Easy way to spread information quickly.
Cons
Short message platform - not suitable for detailed or complex messaging