Although I believe Jaiku has a better format and function than Twitter, I still don’t see the extended purpose beyond a fad. Posting multiple times a day is just plain stupid. Who cares when someone eats or sleeps?
This can be used for displaying some basic ideas, thoughts, or happenings for long distance friends to see. There can be some limited business use for some who want to display things to multiple business contacts that subscribe.
Ultimately, anyone that wants to contact someone should just use email or a phone. The time consuming nature of these mini or micro blogs make them inefficient to use. Time will tell if this tool is just a fad.