The foundation of the American legal system is contract law, primarily to protect private property which capitalism depends on. The terms and the conditions of those contracts, which courts uphold, keep mankind's dark side under control.
So, lawyers probably have a difficult time on Facebook. The social network's ethos is PG-rated. This Brian Carter and Marketo document in their amazing ebook "Contagious Content: Why People Share On Facebook and Why They Share It." Here you can read it, at no cost. That okay-for-universal consumption makes the Facebook platform ideal for advocacy, branding and actual selling.
The wholesomeness is reinforced with buttons for "like" and "share." As Carter/Marketo point out, there is no "dislike" button. Lawyers have been probably itching to have a "question that" button. Well, they might come to see themselves as having the moral obligation to lobby Facebook to install that kind of button.
The payoff to society can be profound. From the get-go, human beings around the world would be trained to think critically. For most of us, that ability isn't developed until graduate or law school. Why do 1Ls, some from elite prep and undergraduate institutions, have to be shamed into learning not to assume anything? Usually it's takes two semesters to get the hang of questioning everything.
In addition, that sort of button could tame the excesses of opining. That's because posters would anticipate being challenged with the "question that" click. Being the recipient of 200 "question that" clicks (the average reach of each Facebook member) could chasten even the most free-wheeling commentator.
As a social network, Facebook is really controlled by its users. Lawyers can leverage that and have the platform move beyond a Disney worldview.