A drug-crazed man runs up behind a woman in San Francisco's Marina district and pulls her to the street as he tries to wrestle her purse away.
A group of young men surrounds a commuter on a Muni bus at Fifth and Market streets; they point a gun at him and demand his iPod.
A hooded man yells at customers in a pizzeria in Oakland's Oakmont neighborhood to put their wallets on their tables, as his partner waves a revolver.
More than 40 robberies occur every day in the Bay Area - and they are happening far more often than just a few years ago.
While recent high-profile restaurant robberies have citizens calling for police to crack down on commercial holdups, the total number of robberies in the nine-county region was up nearly 40 percent in 2007 compared with 2004, according to the FBI's most recent figures.
Some of the worst spots are busy hubs for commuters and shoppers, including the areas around the 12th Street BART Station in downtown Oakland, and San Francisco shopping districts at Fifth and Market streets and the Metreon at Fourth and Mission streets, according to a Chronicle analysis.
"Robberies are the soup du jour of crime," said David Kozicki, deputy police chief of Oakland, which has been hit hardest by the recent takeover robberies, in which armed thieves force customers and employees of restaurants to hand over their money. "I've heard from cities around the nation: Robberies are getting worse."
The Bay Area violence follows a national surge that some experts fear signals the end of a long downturn that began in the 1990s and has allowed once-crime-ridden areas to grow into trendy neighborhoods. Now some of those areas are starting to see old crime problems returning.
The Chronicle examined location records of more than 30,000 robberies in San Francisco and Oakland since 2004, as well as statistics for other Bay Area cities, and found a gloomy outlook:
-- Between 2004 and 2006, robberies spiked in the region, going from 11,264 a year to 15,698, then leveling off in 2007 at 15,646. Bay Area-wide statistics from the FBI aren't available for 2008. But, running counts in San Francisco and Oakland show both cities' numbers are higher this year.
-- Strong-arm robberies, in which the assailants used only bodily force, are the most prevalent. But in both San Francisco and Oakland, the percentage of robberies involving guns has crept up since 2005 - from 30 to 39 percent.
-- IPods, laptop computers and fancy cell phones are such hot items for robbers that some investigators suggest the increasing prevalence of these expensive, easy-to-sell accessories in public places may be a driving force behind the robbery surge.
-- Some of the areas that have seen the biggest increases in robberies are up-and-coming neighborhoods that had seemed to have risen above historical crime problems. These include Oakland's Rockridge district and neighborhoods in the lower hills, such as Oakmont and Glenview near Park Boulevard, and San Francisco's Glen Park.
Criminologists warn that the faltering economy probably will make matters worse.
"The steep economic downturn of 2007 and 2008 portends a crime rise that may dwarf recent increases," wrote University of Missouri-St. Louis criminologists Richard Rosenfeld and Brian Oliver, in a paper presented at a national criminal justice conference in July. "Local communities should plan for new crime increases in the years ahead."
San Francisco's biggest hot spot is the intersection of 16th and Mission streets, where police say drug-dealing activity and the heavy traffic coming in and out of the BART station combine to offer a perfect opportunity for muggings. There were 58 robberies reported there during 2007 and the first half of 2008. More than 70 percent of these were strong-arm robberies.