Fantastic post! I think Facebook will propel us into mainstream adoption too. The company understand promotion, and how to introduce people to their products. Not to mention merchant adoption will probably be a given. Considering Facebook is the largest social network in the world, I suspect many brick and mortar store both big and small will start accepting LIBRA, just to get all those Facebook users into there restaurants and shops. I imagine a great deal of websites will also accept the coin for the sheer purpose of generating sales and attracting users from the largest social network in the world.
I think the downside is the privacy issues. I also think the governments and banks are getting worried now that a HUGE player is entering the space. There are already several questions being asked by lawmakers all over the world. I really feel this is going to usher in all kinds of regulation. I just hope we don't see over-regulation!
Good news is this ushers in mainstream adoption, bad news is we'll probably start to see a lot of government oversight and incoming regulation.