I just had a flashback to the Lollapalooza 2003 show at the Marcus Amphitheater a few years ago. The Milwaukee Summerfest grounds were fenced off for some other event, but the crowd at Lollapalooza was huge.
I got to the show just before Chris Cornell of Audioslave came onstage. He seemed miffed that the crowd didn't bow down to him as soon as he walked on stage. After a couple of songs, nobody was standing. He said something like "Milwaukee, get off your fat asses, and cheer!" That went over really well. Thousands of fans were ready for Jane's Addiction, and I guess that he figured it out when everyone sat down after five minutes of Audioslave.
Since then, Lollapalooza has not come back to Milwaukee's Summerfest grounds. It may happen again, but we don't know.