Oakland police appreciate the help, said Officer Johnna Watson, a police spokeswoman.
"We are all striving for the same goal, and that is reducing crime," she said. "The security companies are an extra set of eyes that allow the community to be empowered."
Putting more police on the streets is the city's top priority, said Sean Maher, a spokesman for Quan. There are now 615 officers patrolling the city of roughly 400,000 people -- down from a peak of 830 officers in January 2009, according to police records.
"When communities get organized and rally around a cause like public safety, it is incredibly effective," Maher said. "It is unfortunate that people feel forced to do this. We want a fully staffed Police Department."
No substitute for police
Chuck Wexler, head of the Police Executive Research Forum, a police think tank in Washington, D.C., said private security patrols are "a sign of the times."
"Cities are cash-strapped, and they are finding it difficult to keep up with the costs of a municipal police force," Wexler said. "And if you want more police, you really have to ask yourself this question: What are cities prepared to do?"
Still, Wexler said, private security companies are no substitute for a competent police force.
"When you are talking about municipal police, you are talking about public officials and holding them to a high standard," he said. "If private security is involved, they should be held to an equally high standard.
"When there is an emergency kind of situation, there is nothing better than a good police officer, and there is nothing worse than a bad police officer," Wexler said. "The same is true for private security."
In Crown Ridge, a collection of homes near Merritt College with sweeping views of the Bay Area, 150 members of the neighborhood association started paying for private patrols in May.
Since then, there's been hardly a whiff of crime, said Nancy Safford, a member of the association's public safety committee.
"Both in terms of amounts and seriousness, (burglaries and break-ins) were escalating," Safford said. "What we were observing was at least two to five cars a day drive through the neighborhood that we were fairly confident weren't visiting the neighborhood, but were casing the neighborhood -- and that has completely stopped."
Safford, a retired mortgage banking executive, said the patrols have contributed to "a rebirth of our neighborhood."
Crime "put fear in us," she said. Now, she said, "families are out, kids are out, people are walking their dogs. We have a better sense of community and a feeling of peace, or calm, and security."
One city councilwoman said all residents are entitled to such peace of mind, but that they shouldn't have to hire security guards to achieve it.
"Oaklanders deserve more safety, and to the extent that citizens can generate it for themselves and their neighborhood, I applaud that effort," said Councilwoman Libby Schaaf. "But it does not excuse the city for failing to provide the most basic element of government. It is not a substitute."