Is that "expected" in the mathematical sense? As in, probability of my actions having the consequence that N animals are saved, times N? How do you work out that the numbers work out in such a way that N equals the number of animals I would have eaten? That strikes me as an unlikely coincidence.
It's not a coincidence. People farming meat animals do so because they expect to be able to sell the meat. If they consistently find that they can't sell it all, or have enough surplus floating around that the price drops and underperforming farms can no longer economically stay in the business, then some farms will shut down. If you've eaten 40 hogs in your life, then you have generated demand for 40 hogs. If there's a farm that had produced 40,000 hogs' worth of meat in your lifetime, then it takes 1,000 people like you to support that farm. It's a problem of collective action to get the necessary number of people to quit patronizing it, but that sort of thing is relatively elementary for LW.
You seem to be assuming that meat farming scales linearly in most respects with the number of people consuming the meat. I'd question that assumption, and assume instead that there are marked threshold effects.
Possibly 1000 people swearing off pork would instead have the effect of driving that same farm to a ruthless cost-cutting program, so that it could keep up its volume by selling at lower prices; this would likely be to the hogs' detriment, since they are the "stakeholders" least likely to raise a politically effective complaint about such changes. And frankly, given what I know of the industry, this is a scarily plausible scenario.
I have noticed that among philosophers, vegetarianism of one form or another is quite common. In fact, I became a vegetarian (technically a pescetarian) myself partly out of respect for an undergraduate philosophy professor. I am interested in finding out if there is a similar disproportion in the Less Wrong community.
I didn't request that this go into Yvain's survey because I want more information than just what animal products you do or don't eat; I'd also like to see nuances of the reasons behind your diet. There are a lot more shades than carnivore/vegetarian/vegan - if you want to be a vegetarian but are allergic to soy and gluten, that's a compelling reason to diversify protein sources, for instance. I'd also like to hear about if you avoid any plant foods (if you think they're farmed in a way that's environmentally destructive or that hurts people or if you have warm fuzzy feelings for plants, maybe). Here are some questions that come to mind: