The Facebook Wall is probably the most famous example of an activity stream, but just about any application could generate a stream of information in this format. Using a common format for activity streams could enable applications to communicate with one another, and presents new opportunities for information aggregation.
Remember Mash-ups? I recall the great wide wonder of putting together web pages that used ‘services’ provided for free through APIs published out to anyone who wanted to use them. There were many at one time, some still exist and others have been culled out. But as newer social networks begat yet newer ones (MySpace,Facebook,FourSquare,Twitter) none of the ‘outputs’ or feeds of any single one was anything more than a way of funneling you into it’s own login accounts and user screens. So the gated community first requires you to be a member in order to play.
We went from ‘open’ to cul-de-sac and stovepipe in less than one full revision of social networking. However, maybe all is not lost, maybe an open standard can help folks re-use their own data at least (maybe I could mash-up my own activity stream). Betting on whether or not this will take hold and see wider adoption by Social Networking websites would be risky. Likely each service provider will closely hold most of the data it collects and only publish the bare minimum necessary to claim compliance. However, another burden upon this sharing is the slowly creeping concerns about security of one’s own Activity Stream. It will no doubt have to be an opt-in and definitely not an opt-out as I’m sure people are more used to having fellow members of their tribe know what they are doing than putting out a feed to the whole Internet of what they are doing. Which makes me think of the old discussion of being able to fine tune who has access to what (Doc Searles old Vendor Relationship Management idea). Activity Streams could easily fold into that university where you regulate what threads of the stream are shared to which people. I would only really agree to use this service if it had that fine grained level of control.