If you're not up on Cloud Computing, this site provides TONS of information and sites to visit to see the cloud in action. It's one of my absolute favorite sites to see what's on the horizon for cloud computing (no pun intended).
I used AirSet cloud computing in the past with the staffs of Schools #65 and #95. The primary reason was to create a shared calendar. It worked really well in both locations mostly because they were only asked to use the calendar feature. More advance/adventurous users took advantage of the other apps including text messaging, file storage and sharing, committee to do lists, and iCal integration. It has changed quite a bit since then.
Ah! You've been doing your homework young Jedi! Do we want to apply "some structure" for example ELA8_xxx; use the more popular tags that are recommended when creating a post, or do we let it all evolve?
"I tend to use the tags that are provided when I tag in Diigo. Is there something I am missing by not evolving our own tags?"
Oh, no not at all. I was thinking down the road when we get teachers hooked on Diigo. Let's say Teacher A wanted to search through his schools' group for ELA content. If the group added ELA_ or Gr8_ as a prefix that might simplify his search. So, in this scenario the provided tags would serve as a base and the prefixes would allow for faster more refined or focused searches.