[rquantz]

the very frequency with which the Farmers' Market is now held in Union Square... might be construed as little more than cover for crowd control, have as it does the effect of making this space all but inaccessible to protesters.

Not saying your argument is unfounded, but may be overstated. I do most of my grocery shopping at union square, and there seems to be a protest there about 30% of the time. I'm sure some people get turned down, but it is clearly accessible to protesters often enough that there are basically permanent police barriers there.

[embarcadero]

Yes, but how many of these are rallies (with people speaking)? Even though the south end of the square is usually free, including on market days, Parks will tell you that they do not issue permits when the farmers are in the other parts of the square. Ask them why they issued one to, say, March Against Monsanto, and they'll say that event was "grandfathered in" (ie, has been happening for several years). (And ask MAM and they'll tell you it was a huge hassle for them as well.)

Meanwhile, on the north end of the square the city is privatizing park space: http://www.nydailynews.com/life-style/eats/restaurant-union-...