If all you need is speed, you should be programming in C in the API of your web server. If you need speed, and lots of it, directly programmed server modules are the way to go.
But speed isn't all. If a scripting language can get 90% the speed of a C module in 1/4 the development time, then you can afford more machines to run it on, if you even need them. If it's 1/10th or 1/20th as fast, then the development time for the C module will be worth it.
I've found PHP and ASP to both be as fast as you can get to programming the direct API for a module without actually doing that, and they both work well. ASP's only real downfall is that it's tied to a proprietary OS that seems and I'm not sure of viability over long periods of time (20+ years) of closed source projects.