DESCRIPTION:
Code used in this demonstration:
http://pastebin.com/RzA84qxU

The reason my FPS drops so low (but still playable!) in the middle is because I basically SPAMMED the blurring shader, and this was multiplied by the number of blurred entities on the screen. I COULD disable blur-stacking (which isn't even noticeable anyway) and essentially make this cost nearly nothing in FPS.