I'm using the workspace for more creative things. For example: A friend of mine began writing a short story (of sorts) on her new workspace and then shared that partial story with me (so that I could add to it). Now, I was notified that she had shared a document with me however that original notice was the ONLY notice that I've received...even though we've each made additions or changes to the document at least twice over the period of a week or so, I've received no other activity e-mail. And, yes, I have that box checked on the workspace.
Naturally, since I've not been notified of any activity, I try to log in every day or two. I've only discovered the 'activity' by accident — rather than because of 'activity e-mails.'
Even from a non-business perspective, people should be notified of any and all changes to a document regardless of the number within a 24-hour period. Otherwise, this "workspace" concept is, essentially, a waste of space.