Why does twitter exist?

I have wondered several times why do we have a plethora of communication mechanisms around us. Why do we have TV, radio, newspaper, books, magazines, phone, fax, sms, snail-mail, email, text chatting, video chatting, video conferencing, traditional blogging, social networks, RSS feeds, micro blogging and of course, good old face-to-face communication, all existing simultaneously in our lives.  The core need is a simple one i.e. to communicate one's thoughts to another person. So why was there an evolution of a host of different methods and why do they all continue to co-exist and thrive. The most recent and striking example is twitter. Functionality wise it can easily be replaced by Facebook or a traditional web forum or even email and yet it has developed a massive user base of 105 million. There has to be an explanation behind its astonishing growth rate of 300,000 users per day!

The reason behind the growth of these services is a basic one - variation in human needs for information dissemination and information consumption. Lets look at how we can categorize those needs -
1) Size of target audience - This is the simplest and most obvious one. Mediums like TV, radio, newspapers, websites etc are sustained by the need to reach a large and geographically spread out audience which cannot be communicated through more personal channels.

2) Size of content - Size of information to be communicated is another obvious factor and it creates demand for low effort per communication kind of mediums. Eg - To communicate a project's roadmap, a manager prefers to mail it to his team rather than talk to each one individually.

3) One/Two/Multi way communication -

4) Level of expression needed - People need different levels of expression for different kinds of information. Eg - For responding to a user poll, a sms reply is enough. You can communicate the same information through a phone call, but that would be an overkill for the low degree of expression expected. However, for birthday wishes to close friends personal visit/phone call is preferred.

5) Personalization and confidentiality - For messages intended for a group of friends, social network/micro blog is preferred. For personal messages email, sms, phone etc are preferred.

6) Synchronization/Interactivity - The time difference between a message and its reply is an important factor which is not very obvious at first. For messages which require urgent response, personal meetings/phone calls/chatting are preferred. For messages which can tolerate a time delay in response email, social networks are preferred.

7) Cost of distribution - Snail mail, email printout, and fax all serve same purpose but snail mail is still the most common method used in rural areas. Getting and maintaining a fax machine or printer is a costly option for these places.

8) Time constraint -  Now lets come back to original question of twitter. The novelty introduced by twitter is that it forces users to stick to 140chars limit and change the content of next tweet. This enables people to talk about variety of different topics without spending too much time on a single one and readers accept these grammatically and spelling wise incorrect messages since that is how medium delivers content.  It allows time-crunched celebrities to express themselves very conveniently. This led to massive adoption by celebrities which in turn led to twitter's growth.

Each combination of above factors produces a unique set of requirements. Whether a medium corresponding to these set of requirements actually exists or not depends on the potential market among consumers and producers for these requirements and the cost of implementing them.

Innovative new mediums of communication come up when either a new potential need is identified(eg need for social networking), a new communication platform/protocol comes up(eg radio in 1890s, email in 1970s) or some of the existing mediums are combined in interesting ways(eg fax). Lets all eagerly wait to see which of these lead to rise of next big thing in communication.

*The motivation for writing this post comes from request by a close unnamed friend :) . Some of the ideas expressed here are influenced by a talk given by Paul Ip(http://www.linkedin.com/in/paulip88) at Microsoft Research and by an interview between Anand Mahindra(MD, Mahindra group) and Steve Ballmer(CEO, MSFT).