Just a few quick notes:

• G+ is heavily centralised and from Google; a Mine would be run by the user, on their own platform.
• G+ is dependent upon Google logins for relationship management; that’s not bad, but it goes with the ‘centralised’ turf.
• G+ is a webby experience, not feeds-based. That’s actually very cool, and something the Mine ought also to be doing.
• G+ sharing technology is relationship-centric; Mine-sharing is purely data-centric, something that Adriana got exactly right in the design.

The last one bears some explanation: people at the moment are using “Circles” – technically a very Mine-like concept – but what is happening is that they are spending time faffing with the Circles and who-is-in-which rather than concentrating on their data.

In a Mine however, you tag the data on one side, and you tag the relationships-likely-to-be-interested-in-thusly-tagged-data on the other; all messy the arguments about “nested circles” and the administration and structuring of relationships just vanishes, whilst the Mine’s hierarchical tags (tag picture with “merlot”, tag friend with “wine”, friend gets picture) ensures the actual functionality that the nested-circles folk want, is possible.

What Google has implemented in G+ is very good; however with the approach they’ve taken there’s the risk of spending all your time categorising your relationships into Circles, and none of it fine-tuning who can actually see what data.