People keep sending me interesting new blogs. Take ThreeDimensionalPeople, for instance. Authored by Stephen Johnston, a London based Nokia employee, it's got all kinds of nifty stuff to read.
Presence: A Red Herring? is a rant on the idea of "just adding presence" to mobile phones. Stephen points out a bunch of the problems associated with today's presence implementations, and proposes to solve them by limiting the data made available, making it effortless to use, and making updates asynchronous (ie. when the publisher chooses, as opposed to context change). That's essentially what iotum has done with Talk-Now — we've limited the data by confining it to a business application space, and made it effortless by driving everything from context. Context updates do need to be recorded in real time, however, even if the presence information isn't published in real time.