I still think a lot of this depends on your availability requirements. I don't think I could run an S3 service at the scale AWS does with higher reliability, b

I still think a lot of this depends on your availability requirements. I don't think I could run an S3 service at the scale AWS does with higher reliability, but I do believe I can run a pool of redundant HAProxies with higher reliability, and in fact we already run pools of HAProxies for other reasons so we have quite a bit of operational experience with it. If my company had three engineers I certainly would not go this route, but if you are big enough to have a dedicated ops team that already has experience with this sort of thing, you can architect something that is more reliable than just relying on S3 alone.