In his column in today’s Washington Post, media critic Howard Kurtz chronicles a Twitter episode that showed how important it is to look before you tweet. (Item at the end of page 3 and the jump to page 4.)

On Monday, “Nightline” co-anchor Terry Moran tweeted that “Pres. Obama just called Kanye West a ‘jackass’ for his outburst at VMAs when Taylor Swift won. Now THAT’S presidential.”

Obama let the jackass comment slip during an off-the-record portion of an interview with CNBC’s John Harwood (Full video minus “jackass” here). The feed was available to other news outlets, which is how Moran caught wind of it at ABC, and immediately tweeted the exchange. CNBC objected, saying it broke the ground rules of the interview.

“Moran quickly un-tweeted his comment. Except by then it had already been widely re-tweeted. You can’t put the toothpaste back in the digital tube,” Kurtz wrote.

Another lesson might be, if you’re the president and you’re mic’ed up, you shouldn’t make any comment you don’t want broadcast — even if you’re right on the money.

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Alexandra Fenwick is an assistant editor at CJR.