That story is a little suspect. Someone had been posting that story on message boards long before Murdoch did it. The story was very irrelevant, it did not get many responses on his page. A young person just posted it on the media portals. Murdoch is not known for shorting stocks, I think it was more of a personal attack against FB than anything else. A young person just made a big deal out of it.
People really need to understand what they are reading before they jump to conclusions. The Pew report states that about 92 percent of teens still use FB and that most african american teens made up a large percent of the growth on Twitter while white teens still prefer FB. Other studies also suggest that a large number african american households are run by single parents. This implies that both parents may not be involved in their teens lives as are white parents. The point is that there are other factors to consider here before one can draw a conclusion about this report.