[anApple]

The webserver will only do computations which data they get from other services (memcache, etc...). They will never fetch the data locally, so there is no local bottleneck except the local bandwith and the efficiency of the code, thus the cpu.

[leej]

then only logical reasoning behind is cheap machines for webservers and very powerful ones for "data" servers. otherwise network bandwith is only a fraction cpu-storage one.