Well, it may have popularized the phenomenon of holding lit cigarette lighters at rock concerts.

It was pouring rain in Bethel, New York on Friday, Aug. 15, 1969. A thunderstorm had moved into the area, drenching 400,000 people at the Woodstock Music and Art Fair.

As folk musician Melanie Safka took the stage just shy of 11 p.m. that night, the stage announcer instructed the audience to light candles "to keep away the rain." The candles had just been handed out to the crowd in a mass distribution. The drizzling rain dampened the candles, and attendees whose candles were extinguished (or didn't receive a candle) raised their cigarette lighters in support. The net effect was astonishing from the stage, Safka recalled.

The experience inspired her to write a song: "Lay Down (Candles in the Rain)". That song, released in 1970, reached No. 6 on the Billboard 100 chart, and Safka's fans commemorated the event by holding lighters up at her concerts. Today, Safka's LinkedIn page declares, "My appearance at the 1969 Woodstock Festival prompted the now-common phenomenom of signaling an artist for an encore by holding-up some form of light...(at Woodstock it was candles; which then emerged into cigarette-lighters, and now onto cellular phones! ~It inspired my writing of "Lay Down, Candles In The Rain)!"

I don't know that it was a turning point in and of itself, but it certainly represented a change in American culture at the time. Or, put another way: The change had largely already happened (as evidenced by the enormous crowd at the festival) and the event itself was a tremendous public affirmation of that fact. Being one of the first and largest symbols of the counter culture of the time, it's rightly associated with that change in the first place.