We don't have the hubris to think Clearspace is going to reshape email practices in any profound way. After all, email is still a remarkably efficient medium and still has a "if it ain't broke" layer of protection around it from all its users (it's easy, cheap, standards-based, supports HTML, etc.). That said, we do think it helps with one of the big gripes we heard during the Clearspace design process: knowing who to copy on emails.
The "Who to Copy?" Phobia is a Fear of:
Copying people that don't want emails. The fear that recipients will just delete the emails and/or get upset about being copied on something useless.
Not copying people who should be. The fear that recipients will feel ostracized or controlled if they're not involved.
In either case, the onus is on you-the-sender to come up with the perfect list of email recipients (not to get into who is on the cc: list v. the main list) and not upset the balance of cultural protocol and politics.
Shifting the Responsibility
By putting the content into the medium best suited for it (news in blogs, "living content" in documents, questions in forums, etc.) and by having a very rich notification system (rss, IM, private messages, etc), you can shift the onus to the recipients and rest easy, knowing that the right people are notified and kept up to date. No more awkward water cooler confrontations about why they weren't included on an email, and if it's a subtle indication that they'll soon be out of a job. Just say, "Update your notifications, Ted!"
The email problems Clearspace hopes to chisel away run much deeper than this (workflow, versioning, etc.), but this is one of the "aha!s" that have come out of the User Acceptance Tests and early demos we're doing, and it's fantastic to watch people get excited about how Clearspace can help them.