I was going to call this "groupware," but that tends to drudge up imagery of Exchange, Zimbra, Horde, etc. I am not talking about that kind of groupware. Think more like Facebook. An infrastructure that would allow University individuals to create groups... any group. And swap membership in and out.
That would take a lot of plumbing. A lot of middleware work to make happen because the infrastructure would need some seriously well-though-out APIs to make the information available to any and all systems.
But no one cares about middleware, the important part is the services built atop the middleware. The obvious first service is a web application that allows persons to create groups, join groups, leave groups, post messages to a forum for the group, post pictures to the group, etc. But it's not just for "social" groups like the group dedicated to the people who like the television show Scrubs. It can also be used for professional groups — the iTunes at Case group, the Identity Management Group, the Case Daily implementers group, etc. Pre-populated groups like "Spring 2006, ECES 131 group", Case Archery Club, Film Society, etc.
With open and available APIs, other services could leverage the group membership. Such as the hypothetical wiki farm i.e. being able to setup a wiki that was world-readable but only editable by the people in the iTunes@Case group or could only be accessed by people in the Identity Management Project group. Create blog entries that only people in your "Friends" group could see. Create blog entries that only people in the Identity Management Project group could see. Share photos that only people in your "Friends" group could see. Share files that only people in the iTunes@Case group could see.
The reason this gets my #1 most wanted ITS service is because it can raise the tide of many of the other offered services. But implementation of such a service is tricky because without well defined and open APIs, the number of services available to use it becomes limited thus the usefulness of the service quickly negates itself.