This discussion at New (Sub)Urbanist and in the print version of the Chicago Reader is an important one. I'd like to agree with the comment that the commercial photography prohibition in Millennium Park won't last, but I'm not so sure.
I think a related issue is the diminishing numbers of public and commercially-owned places that refuse to allow flyers to be posted on their premises. Got a rock band? A fundraising event? The number of public and public-like spaces where you can distribute your information is limited.
Libraries have bulletin boards for this information, but their size and location vary among branches. Many shopping malls don't allow leaflets from the public. Starbucks prohibits any materials from being left in its stores. Barnes & Noble used to allow flyers in their lobbies, but no longer. Same with Borders.
Last year, I tried to post flyers for a non-profit event at a Starbucks. I was told "no." I wanted to drop off copies of an independent newspaper at Borders. They said "no." Both times, the employees felt really bad about turning me away. Their common sense and presence in the community told them this was no biggie. But, corporate policy overrode them. Would corporations benefit if they began thinking of customers as their stores' neighbors rather than as consumers?
I understand that the Millennium Park issue is a true tax-supported public space and not a commercially-owned space like I'm (mainly) complaining about. For this, I think the copyright issue is especially egregious. But, more and more often, commercial spaces function like public spaces. And, by looking at the flyer issue we can see in a subtle way how locally-owned coffee shops and bookstores function differently in our neighborhoods.
Because I don't have any independent bookstores or coffee shops in my neighborhood, I ended up posting my flyer and distributing my newspaper at my local YMCA (a non-profit organization.) They have a giant bulletin board in the women's locker room for flyers, and they provide a space for independent newspapers. Could their attitude have anything to do with their mission statement: "We build strong kids, strong families, strong communities"?