Neighborly relations have declined in the U.S. since the 1950s, for reasons sociologists don’t quite know, and lack of local ties is bad for crime and a community’s ability to organize for its interests.

Some 28 percent of us don’t know any of our neighbors’ names, reports a 2010 Pew survey; it’s particularly pervasive among younger and lower-income people.

“The biggest barrier is just a perception that we should not be involved,” said Keith Hampton of Rutgers University. “We fear having people intrude in our lives.” But that comes with a risk.

Knowing neighbors can help defuse conflict before it gets ugly. “If someone leaves their dog out too late barking, then that’s Joe, it’s not some random guy,” said Bob Borzotta of neighborsfromhell.com, a chat room for disputes.

Though technology is partly responsible for making neighbors less relevant (it lets folks get social support from afar), it also is helping revive neighborly ties. Several social networking sites are dedicated to connecting neighbors; One site is Nextdoor.com, which has more than 1,900 neighborhoods. Its aim is not social but to solve practical problems, like finding a lost dog or organizing a block party.

That’s not to say all neighbors should be best friends.

Respecting boundaries is vital, Borzotta added.