Finally started to slow down with several hundred workers, 123 speed, 101 life, 154 sight, and 253 land. Was pulling in about 200 resources/second and couldn't keep up with the souls flying in.
To all of you people complaining that kreds are ruining the site. This game had a cash shop before it ever came to kongregate, so you can't blame kreds or kongregate on this one. If you don't want to buy the damn upgrades then don't. It really is that easy.