I was accepted quite early at SF but I was pissed off by a rejection from one of their reviewers that didn't like a green foliage background. "Change background", the dude told. Hahaha. That image was accepted everywhere else, included iStock. Later, I made about 0.5 euro at SF while I made 4x (oh well 3x because of the $/Eur ratio) as much on iRockstock after being signed up there for just 3 weeks. Veer (a contemporary startup) made about 3-400$. I deleted everything at SF after that since my gut told me they will never make it. Probably it was overkill after 2-300 shots but if you employ ignorant reviewers, there is no hope. I wish them the best. Next!

sorry but I am not following your 3x more at iRockstock once you have 1 sale there

p.s: I am supporting both agencies