MICHAEL LETWIN, a lawyer living in Brooklyn, went to sign into his Facebook account, as he does almost daily, and received a surprising — and unpleasant — message.

“Your account has been disabled,” it said. “If you have any questions or concerns, you can visit our F.A.Q. page.” Mr. Letwin, who besides his personal page also helps administer a Facebook page for the group Jews for Palestinian Right of Return, clicked onto the F.A.Q. page and found a reference to Facebook’s community standards, none of which he felt he violated, along with the option to appeal.

He did. And then he waited. And waited.

Mr. Letwin’s situation is not unusual, or new. The question of what role social media companies should play — a hands-off observer that steps in only in extreme circumstances, or a curator that decides what goes up and what comes down — has long been debated.

Recently, Twitter refused to allow posts with links to videos of the beheading of the American journalist James Foley. Facebook is involved in a battle with drag queens whose accounts were disabled because they used their stage names in their profiles. Using anything but your real name is a violation of the company’s rules. The furor led this week to a meeting with Facebook representatives and a news conference called by a San Francisco supervisor.