Twitter and SMS
Back in the good old days of Twitter the length of a tweet was limited to the length of an SMS. The aim was to make it possible for people to tweet and have conversations using GSM phones. With short messages we could leave the keyboard behind and read messages on our mobile phones.
Jaiku was similar except that it was more advanced, having an app that played well with Symbian devices. With time, and the advent of the iphone and ubiquitous data plans so platforms like Twitter and Jaiku could add images and more. With time Seesmic experimented with video and instagram with images. Instagram thrived because it made uploading and sharing images fast and easy, even in the days of limited bandwidth.