I live above Ocean Avenue in Santa Monica and have a bird's eye view of parking cheaters. The curb is divided between disabled-only parking and regular metered spaces.
As Donald Shoup notes, a driver with a disabled placard can park anywhere free, an issue in which I take a special interest because my late mother needed special parking rights.
From more than six years' worth of observation, I can state confidently that only a small portion of drivers with the blue placards are actually disabled. The cheating is rampant and disgusting. Even though the placard abusers face a $1,000 fine, I have never seen anyone get caught. After parking their cars, the drivers slither out of their vehicles and disappear for hours without a concern.