I'm just pointing out that Mike at Techdirt's "Zero Marginal Cost, Infinite Good" argument applies equally well to empty seats at a concert or sporting event, or to lack of capacity crowd at a museum.
Does it? Can you put an infinite number of people in those seats with marginal cost? I would posit you can't so it doesn't.
By Mike's argument, 1) people should expect to be admitted free under such circumstances, and 2) the organizers should welcome them for the possibility of incidental business (concessions, swag).
And they do. Not everyone, not always, but they do. Remember the last bar you went to that didn't make you pay for listening to the music they were playing?
Obviously, it's a ridiculous argument in the case of a rock concert, particularly because the very same people who condone piracy often recommend that musicians make their living by selling tickets at live performances. But what makes it ridiculous is that there is an obvious, visible security apparatus in place at the concert that will either physically prevent gate crashers, or who will likely get them hauled down to the local police station.
Of course, they are there _only_ to avoid freeloaders getting in. Never mind the limits of people in the venue, the need to avoid altercations, etc.