I just ordered a bunch from here: http://www.starsurplus.com/viewitem.lasso?i=SLEH-00448-BULK-36PK. The shipping is a bit more expensive, but cheaper than free shipping options. Googling around will yield some other sellers with various prices in the same ballpark.
I'm not sure I can get 200 running at once ... will definitely take a lot of USB bandwidth. I'm expecting that multiple machines will be required. I did get 4 running on a raspberry pi 2 @ 320x240 with a high framerate though, so I'm optimistic.
I can't reproduce the checking only once usb port issue. I've got 3 cameras hooked up on each of my USB busses (just a mac laptop) and all of them are located.
As for the glitching, I'm pretty certain that is a just a case of the USB bus bandwidth getting saturated. I can run 4 cameras at 30FPS @ 640x480 off two usb busses, but if I try to do the same using a single usb bus and a hub, i get all sorts of malformed packets and glitchy images. Turning the resolution of fps down allows more to be on the same bus without a problem.
