Does "Account" belong in the Identity Model?

Last week at my day job we made some tweaks to the model such as changing a many relationship to a single relationship, changing the top box from Privilege to Entitlement, and relating Sponsor to Digital Persona instead of Subject. We also discussed whether or not the concept of Account belongs in the model. We ended up the meeting agreeing that Account is a kind of Entitlement and doesn't warrant its own box. However, as I tried to update the diagram and descriptive text, I couldn't make it make sense. So, against the majority in the meeting, I stuck Account back in. Please look it over and comment about whether or not Account should be in or out -- I'll need your support if I'm to convince others that Account should stay in.