Revolutionary technology: Google Glass / AP

A group of patrons are thought to have become upset, believing Sarah Slocum was filming them without their consent

It has been billed as a clash of cultures between tech workers and their fellow San Francisco residents. But now the tensions have spilled over into violence.

A woman wearing Google Glass was attacked in one of the city’s bars on Friday. Sarah Slocum, a tech writer and social media consultant, claimed on Facebook that she had been “verbally and physically assaulted” for refusing to remove the hi-tech specs, which were snatched from her face by a man who ran from the bar. She recovered the $1,500 (£900) device from her alleged assailant, but returned to find her purse and smartphone gone.

Prior to the incident, Ms Slocum said she had been happily demonstrating Glass to “normal, excited and curious individuals” at Molotovs, a punk bar in the Haight-Ashbury area. But one group of patrons are thought to have become upset, believing she was filming them without their consent. As the evening turned confrontational, Ms Slocum did indeed record some of the fracas in clips which she later posted on YouTube. The group, she says, threw “dirty, wet bar rags” at her; the confrontation reportedly became violent when one of her friends threw a punch.

The influx of highly paid tech workers to the city has caused friction with existing residents, who blame Silicon Valley commuters, from companies such as Google, Apple and Facebook, for rising rents and rapid gentrification.

Locals have expressed concern that the rich professionals are driving up house prices and – inadvertently or not – driving out residents.

The Google buses, which often stop in spaces supposedly reserved for public transport, are a particular point of contention. This growing fleet of unmarked luxury coaches carries some 14,000 people on their 35-mile trip from the city to Silicon Valley and back. Since the search giant introduced the buses a decade ago, Facebook, Apple, eBay and almost 40 other companies have followed suit. Each new route quickly becomes a corridor of hip clothing stores and restaurants.