In my opinion, the reason behind the abilty to transform twitter into anything you want, may be the "Policy and mechanism separation". (Those who know my 4th year project know what this means!) Unlike Facebook or other social media, Twitter doesn't implement so many policies (other than that 140-character limit!). It only provides a simple message multicasting mechanism to share your ideas. You can build your own policies on top of that mechanism.
As I see it, the only core rules that twitter enforces are,
- You have a queue of messages. (Your twitter account)
- Messages (you can call them status updates if you want), are limited to 140 characters each.
- You publish messages to the queue. (by updating your status)
- Others people can subscribe to your queue. (by Following your account)
- You can subscribe to other people's queues. (by Following them)
- When a message is added to a queue, subscribers also receive it. (Those who follow you, receive all your status updates)
- In addition to the core policies enfoced by twitter, the community have developed some policies (or standards) over time to make it more user friendly. Speaking of terminology, Messages are reffered to as "Tweets".
- In addition to publishing a public message, you can publish a message targeting a specific user. For that, the message is prefixed with @[username]. These directed messages are known as @replies (pronunced "at-replies"). But since @replies are just ordinary messages, other subscribers also receive it. (remember, only core policies apply! all others depend on how you interprit them) But everybody knows to whome this message was sent for, so they will ignore it if they are not interested.
- You can pass a message you received from another, to your followers by prefexing the message with RT @[original-sender]
(RT stands for "re-tweet"). This is like saying something you heard, to your friends while crediting the original person who said it. Again, remember, these are just ordinary messages. Users themselves have adopted these standards on their own.
Companies are using Twitter to advertise about their products. This includes technology giants and even Bakeries (link from @akilakalum). Some people have automated tweeting through the use of sensors and mobile phones so a new message is published every time an event occurs. Even really famous people are on twitter and anybody can follow them. Some I found are Mandy Moore (@TheMandyMoore), Demi Moore (@mrskutcher) and Senator John Mchain (@SenJohnMcCain) and Ravin Perera (@ravinsp) :-P
I have just begun using Twitter. So right now there's no use for me from it other than receiving good links and intersting info from other people I follow. Time to time I also put interesting things to be received by people who follow me. (I don't have so many followers actually!) So if you really don't have anything else to do, follow me on http://twitter.com/ravinsp.
Finally, a one comparison with facebook:
If Facebook is a global directory service, Twitter is a global notification service.