As I already wrote (2), though, I'm not sure if this is a great move for Facebook in the long run. Facebook owns the incredibly compelling core expectation of "easily sharing with friends and family through the Internet". But, for obvious reasons, public posts and comments are preferable for advertising purposes, so Facebook is also trying to eat Twitter's pie.
Problem is, can you be both the place where people connect with their closest connections, and where public discourse goes on? My guess is that you can't, and if this move really succeeds - which is entirely possible - this could be the start of the end of FB's domination of the "privately sharing" space - which is less easily monetized, but much more compelling than the "publicly sharing" one.
(2) http://danmaz74.me/2013/05/16/facebook-hashtags-when-monetiz...
EDIT: some corrections