All the lonely people.
The echo that is so often heard late at night across social networks.
In the latest case, a 16-year-old girl in Maryland learned that one of her Facebook friends, a boy in Oxford, England, was in distress. Late on Wednesday night, he wrote: "I'm going away to do something I've been thinking about for a while then everyone will find out."
The girl didn't know the boy's address. But she immediately felt this was a serious situation and told her parents.
They contacted the British Embassy, who in turn got in touch with Scotland Yard and the local police in Oxford.
All they had was a name. But they worked quickly to narrow the possibilities down to eight addresses.
They sent police to each of these addresses, and within three hours of the Facebook message being written, the boy was found.
He had taken a drug overdose, but was alive.
This story follows the one earlier this year when a MySpace member in New Jersey helped a distressed teenager in Sacramento, Calif. And it comes in the same week that actress Demi Moore and her followers helped a woman in the San Jose, Calif., area after she had used Twitter to announce her suicidal intentions.
Sometimes you don't know who your real friends are.