One of the reasons for the great Facebook IPO flop of 2012 was investors' fears that the social network couldn't monetize its user base.
What good is a billion members, the thinking went, if you can't get a buck from them? Ad revenue can only go so far.
So Facebook has done some experimenting, and late last year, under much of the media radar, the social network unveiled a modest way to pry money from its users: charging $1 to private message anyone that wasn't on your friend list.
At the time, nobody noticed a $1 fee for a service they'd rarely use, but what will people say if that charge is boosted up to $100 per message?