I assume that if HN ever caused them any serious PR damage, they'd pull the plug that day. It's always been made clear that it's a single-server site sitting somewhere that was written as a hobby a long time ago. That kind of nothing cost they're willing to take on indefinitely, but not any serious bad media cost. I've always felt that was the reason for the heavy moderation, especially as compared to the anarchic early days. Even with the salaries of dang et al. expenses are probably a rounding error.