From Social Patterns
Statuscasting is the custom of broadcasting an ongoing stream of status updates to the public or a set of contacts or followers. Similar in concept to IM status updates, statuscasting incorporates the idea of the ongoing feed that can be browsed into the past. It does not necessarily indicate availability at any given point but implies it, in the sense that if you see a recent status update from a friend, you may feel that they are available for contact.
There may be some value in cross-feeding status updates from one system to another. Twitter users, for example, can have their status updates on Twitter become their status messages in their IM clients (or vice versa). Posts to Twitter, likewise, might be broadcast into another service, such as Facebook or Friendfeed or Yahoo! Updates. Be careful how you enable these kinds of connection, however, as the original context may be stripped away and the updates may not make sense or work well in the new context.
For example, Away, Idle, and Available are 80% or more of all IM statuses.
Statuscasting tools, such as Twitter, lend themselves to inventive variations and uses. If you give people a box to type into a button to press, they will discover their own uses for it.
In addition to display of an single person’s statuscast feed, it’s common to provide a way to see a collection of people (everybody, or just the user’s friends) and their most recent updates. These kinds of interfaces may benefit from providing the user an easy way to filter or sort, especially when one person is dominating the combined feed with a stream of constant updates.