The internet has been designed around the concept of pulling information to the user. Users lookup information or interact with a social network or any other web application. The user decides where to go and which information to access. Even applications like email or chat which push information to the user it is still a pull concept since the user has actively enable these application to reach them.
But there are new services getting immensely popular like Twiiter, Identi.ca, StatusNet, Plurk or Foursquare which change that concept around. Here the information just flows onto the internet. The user can access this information midstream or go back into time to see what has happened in the past. Bur the information is not targeted at a specific user but just happens. The user can decide which parts of the flow of information he is interested in and plugs into that part of the stream. He ignores the rest of the streams.
The concept of streaming information onto the internet is a very powerful paradigm which opens a lot of new opportunities for people to communicate to large audiences. They can target audiences without knowing who they are. Interested parties can just tap into the stream where their own interest lies.
The time component of the information stream is another important aspect. A lot of information is only relevant as it happens. Think about news, discussion or discount campaigns. Up until now it was hard to universally communicate time sensitive information without direct targeting specific users like via newsletters or ad campaigns. But these are all broadcasting large audiences who may or not be interested while missing other users who are interested but reached using these methods.
It is just looming under the horizon. Current services like Twitter or Identi.ca are just scratching the service of what is possible when going from pull to push information streams. In the next years services like these will transform to more generic services or others will stand up and fill this gap. The major jump is made when the push information stream is made available for generic use. This could either through standardized protocols or via one or more service providers. Just imagine you are interested in buying an Apple Ipod and waiting for the right offer to come along based on price and location. How cool would that be?