For which identity attributes are personas most relevant, i.e. for which characteristics (e.g. profile, calendar, wallet, social network, etc) would it be most useful for a User to be able to manage duplicate views into the data - each used in appropriate contexts.
My Google calendar is a perfect example. I have calendars for work, for conference calls, for travel, for my sons' hockey teams, and for my wife's work, etc. If asked to share my schedule, I'd choose whichever of the above calendars was right for the context of the request.
Being able to slice and dice in this way would clearly also be relevant for my social network (were I to maintain the full pie in a single place as I do for my calendar - which I don't because no SNS allows me to compartmentalize in the same way). My work persona would define one set of 'friends', my family persona another, and so on. I'd either group these different sets into persona URLs, or group or tag them under some shared API endpoint.
What would personas mean for a wallet? Simply the analogy of how we currently choose a credit card appropriate to the situation, e.g. a company or personal card.
How about for a personal profile? Would I provide the cottage address when I was in 'Summer' persona?
Presence and geolocation (and any other such dynamic identity attribute) seem least amenable to the persona model. I might define different policies over their sharing, or level of detail/accuracy depending on the context, but I wouldn't maintain multiple sets.