Other interventions haven't been met so kindly. For example, last year after California passed a state-wide law banning street parking within 15 feet of an intersection (to improve visibility of pedestrians), some people tried to paint curbs (red curbs mark prohibited parking), frustrated the city was acting too slowly to repaint curbs everywhere. I don't remember if they were ever caught, but presumably they would have received a fine as it caused alot of headaches--it cast doubt on the validity of many parking fines issued after the law took effect as the parking enforcers couldn't know what had been officially repainted, yet.

As for the guerilla bike lane on JFK Drive in Golden Gate Park, that entire 1-mile section of JFK was later closed off to cars entirely. It required a city-wide ballot initiative, IIRC, and was very contentious. But the city government was in favor of it, which may have something to do with why they were so accommodating earlier with the bike lane.