Facebook continues to take it on the chin. The stock closed at another new low — $26.90, down nearly 3% on the day, and -29.2% from the $38 IPO price. Bernstein Research analyst Carlos Kirjner contributed to the slide by initiating coverage with an “underperform” rating and a target price of $25.00. He says that “Facebook’s revenue growth over the next 12 months will at best stabilize, and probably further decelerate, as will growth in revenue per user.” Critics of the social network company say that fans increasingly use it on mobile devices and it hasn’t demonstrated an effective strategy for advertising there. Kirjner adds that “there is very limited, reliable, empirical data on the effectiveness of social advertising.” Wall Street’s souring view of Facebook comes as the company faces an armada of skeptics to its plan to let kids under age 13 join the social network if parents approve. Facebook has said that lots of kids already use the site, and it’s thinking about strengthening protections. “If Facebook is serious about making the site a safer place for kids, it has to deliver stronger controls and education aimed at parents, ant they shouldn’t target kids with ads,” says Consumers Union regulatory counsel Ioana Rusu.