There is a new SharePoint Online Hybrid Architecture Whitepaper that has been published - http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=27580. It is definitely worth a read and has some good stuff. I think it is a good place to start but there is a lot more too this.
I will be working on some SharePoint architecture blogs that discuss this along with general SharePoint Governance and Information Architecture. I have been having way too conversations with clients where people confuse the real spirit of governance making it too authoritative. It is not about locking down SharePoint; it is about setting up business services and service level agreements and then delivering capabilities on them. It is about setting up a real Information Architecture! More to come I promise.