They may have been watched like a hawk, but that still didn't stop spectators from getting their cellphones past security at the Olympic Club.
Most people waited until they were off the course. Others say they were respectful even though they broke the rules.
The cellphone ban follows a series of annoyances during the tour. Phil Mickelson withdrew from the Memorial Tournament last month, citing mental fatigue, but cellphone distractions were also considered an issue.
Crowds arriving at the Olympic Club had to go metal detectors and have their bags searched. At one gate, security collected about 130 phones.
The ban frustrated some fans.
"I don't know how much harm you can do with your phone; it's ridiculous for a practice Tuesday," spectator Fernando Reyes said.
Other fans thought the ban was a slice of heaven.
"You know I was frustrated at first, now it feels so nice," San Jose resident David Norman said.