Reintroduce Megafauna to North America?
Part of it? Sure. But we are the dominant species. The fact that we're sitting here posting about management of other species on the internet should at least help to demonstrate that. (that is, unless monkeys have a highly evolved method of electronic communication we're unaware of - oh, so that's where slashdot moderators come from ;)
Seriously - to think that we're the only species that would wipe out another because we eat them, or because we build houses, or develop ranchland...is absurd. As long as food is available, some animals will eat until they die.
My point is, if humans were to vacate the planet today and leave the other animals to their own devices, there would still be extinctions. I don't think we should totally disregard responsible behavior and go killing every animal in sight, but I think a little thought is in order when we're paranoid about a species of fly vanishing from our world forever.
After all, if it evolved from something, won't it eventually come back (and no, I'm not a foe of evolution)?