The good news is that Twitter is planning to lift its 140-character limit for tweets. But that just raises a different question: why did that limit exist in the first place?

It’s because Twitter started out via SMS. At the time, SMS carriers had a cap of 160 characters on each message, but Twitter reserved 20 characters for usernames. That’s why tweets were limited to 140 characters.

The idea for the micro-blogging service came from Twitter co-founder Jack Dorsey’s fascination with how a city functions in real time. He mapped the city’s support systems — from emergency services to vehicle dispatches — through the lens of the Web.

And guess what that gave him? A rich picture of a city in motion. But there was something missing from the picture: people, the one element that made the city come alive.
Dorsey’s idea of creating a type of digital dispatch service gained momentum when he signed up for a LiveJournal account in 2000. From that point it was a matter of finding the right medium, and that medium happened to be the humble SMS protocol, which in turn brought the 140 character limit.
Of course, a lot more behind-the-scenes work went on before the Twitter we know was born.