Linden dollar

Has anyone know how Linden dollar works and why is it so easy obtainable?
Essentially it could be the same with Steem. In ''Second life'' you can buy Linden dollar and use it in community, which includes paying for scripts, models, donating, trading and so on. How did they get away with it? It was 2003 when it was launched and it has survived this far.
If Linden labs made it accessible to buy with so many merchants, maybe its possible to make Steem as a community digital currency. Steemit could have like a 3D model or wallpaper or any other digital content shop where we can purchase content with steem or steem dolar.
Would that be possible at any point?
I think It would open a door for many digital content creators.