Missed use case:
I'll often suggest to folks that they keep anything they wouldn't mind everyone in the company seeing in the business notebooks, and anything personal (meeting notes, personal to do lists, other personal work related items like HR stuff) in the personal account.
This situation would be broken because of the lack of universals search and access to notebooks.
Couldn't we still have the separated accounts but have one "All Notes" view that we can go into that affords us all these luxuries? If it's some kind of Enterprise requirement that's driving this, you could allow/disallow the ability to have the app boot into that as default view at the Admin level.
The lack of universal search is really killing me. Would anyone ever go to try both Google *Personal* and then Google *Work* when they need to find something online? No.