All of the math is just wacky in the post though - he's comparing peak pageviews/sec/server to Facebook's pageviews/sec/server for a month. Reddit's pageviews/sec/server is 2 using 163 pageviews/sec and 80 servers.
Facebook also doesn't count all webserver HITS as pageviews, whereas most of Reddit's do count.
Beyond that, pageviews for Facebook may eat more resources (CPU/RAM) than Reddit on average due to photo uploading and other misc. things on Facebook. This means a server is working harder at 2pageviews/sec/server for Facebook.
Facebook also doesn't count all webserver HITS as pageviews, whereas most of Reddit's do count.
Beyond that, pageviews for Facebook may eat more resources (CPU/RAM) than Reddit on average due to photo uploading and other misc. things on Facebook. This means a server is working harder at 2pageviews/sec/server for Facebook.