“What is the digital equivalent of…?” is a thought experiment I have been playing myself and with various other people since the early 90s. It asks about the nature of things in the new digital / information world we are creating.
Things are what they do, not what people say they are or how they sell them to you.
So, for example, Dropbox is sharing and synch with version control – it is NOT secure cloud storage and never can be. It has been engineered as inherently insecure because its trick is built on synching the diff, which it can’t do without being able to decrypt your data.
And Facebook is not a social network, it is a proto-identity authority, an anti-controversialist walled garden but ultimately little more than a massively centralised public forums system with over-engineered (and highly dangerous) profiles. The clue is in the ‘social graph’…
Google is likewise a proto-identity authority. It has evolved way beyond search and its ‘mission’ – “to organize the world’s information and make it universally accessible and useful” – once personalised / socialised puts it in prime position to become an arbiter of identity.
What is the core ‘behaviour’ of a system?
That is what it is.