[jules]

Absolutely. A modern quad core $100 processor doing 10 requests per second has about 1 billion clock cycles per request. You can easily lose a factor of 100 by using an interpreted language, another factor of 10 by using a bloated framework, and another factor of 10 by using a DB optimized for disk instead of one optimized for RAM.

Due to network overhead (in performance, but more importantly in complexity when programming and sysadmining) and the speed and size of modern hardware, for the vast majority of sites it makes much more sense to run on 1 powerful box than on 20 small boxes. And even if you do need to scale to multiple boxes eventually (which >99.9% of websites won't have to), managing 10 boxes instead of 200 has advantages too.