Carol: Everyone with their little perspective. Perspective shuts out the universe, it keeps the love out.
As Eliott walks across the hillside where the concert is taking place, you can see nylon dome and bivouac style tents. Tents made with metal poles and nylons didn't come to market til the 70s.
At the end of the film, Michael Lang mentions he's going to California to put on another free concert with the Rolling Stones. He's referring to the infamous "Altamont concert" where the Hells Angels motorcycle gang provided security, which resulted in a number of people being beaten up, two people dying in a hit-and-run accident, one accidentally drowning, and another being stabbed to death.