'Social Media'....a fiat currency of its own?

So, everyone's up in arms over what Twitter/Facebook are doing- I say; who gives them this power? Is this something akin to fiat currencies, where the 'value' is merely an agreed upon value? 

If so, that means YOU can devalue Twitter/Facebook by removing yourself from the equation.


Why would you permissively and willingly give these companies your demographic info? Why do you take stock in their values? Why do you spend YOUR valuable time in a Facebook/Twitter hole?