Furthermore, even as a website aiming to survive some momentary spike in performance - slowing everything down for everyone _can_ be part of a solution to serve more people but fewer things each. People might not normally be willing to wait for more than a second or two for a load; but when they expect or have a sign that things are slower than normal, they might have a little more patience (or just come back to that tab later).

I think people are a little too negative on queues. Sure, really naively implemented with entirely unbounded capacity they're an accident waiting to happen... but you don't have to do that.