I know you're only talking about Veganism as an example of taking control of the situation for yourself, but I wonder if anyone has seriously mapped out total consequence of everyone going vegan, the pros v cons.
For all the savings on cow flatulance, what happens to the now wild domestic cow left to fend for itself, the sheep, the chickens all left to roam the countryside untended. Bees without beekeepers might well die out. Wild boars would essentially return to the country..
Also, if you're hard-core vegan, you don't exploit animals in any way, so no horse riding, no pets, no swimming with dolphins, no alligator wrestling, no donkey rides at Skeg Vegas.
But seriously, a totally vegan society, without immense sacrifice (no just by humans giving up their practices, but also by huge culling of farm animals on a regular basis) is fraught with immense difficulty.