From Social Patterns
When status updates first emerged in the context of instant messenger programs, they were inherently fleeting, temporally tied to the immediate moment and then discarded. It really doesn’t make that much sense to keep an infinite log of Available, Busy, Idle, Offline, and so on for the life of the user or the application. But as other status-capturing interfaces have evolved, the idea of at least maintaining a stream of recent history, and then possibly mixing status reports with other snapshots of online activity has taken hold as a way of displaying presence.
There is still an element of ephemerality to this. One rarely thumbs through days and days of old status updates to find what a specific person was doing or thinking or listening to at some arbitrary point in the past (at least when one is not stalking them), but there’s really nothing to stop these sorts of feeds of personal status updates from being stored, permalinked, catalogued, indexed, made searchable, and so on, even if by custom presence affordances are geared more naturally toward the present moment and the recent past.
(aka Feed, Wall, Stream, Activity Stream, Life Stream)
You can view a person’s vitality as the sum total of observable behaviors they are engaging with oneline or within your system. This may include status updates but it may also include any number of other recordable activities that can be captured via RSS feeds or by polling or scraping their activity feeds across a wide variety of services. This may also be a mix of services within your system or network, or may combine services across the public Internet.
A vitality feed may therefor consist of an aggregation of updates and activities that together can create a much richer sense of what the user has been doing, thinking about, and saying in the recent past.
Services that aggregate vitality online include Facebook, Friendfeed, MyBlogLog, and Yahoo! Profiles.
Individual items in a vitality feed may be referred to as Updates.