A regex of machines? Every odd machine in the first datacenter? Software load balancers? Uh, I'm guessing most places do it much more scientifically than that,

A regex of machines? Every odd machine in the first datacenter? Software load balancers? Uh, I'm guessing most places do it much more scientifically than that, and I would be very surprised if anyone in the top 100 sites is using a software loadbalancer (I only know of Wordpress using nginx http://barry.wordpress.com/2008/04/28/load-balancer-update/ http://barry.wordpress.com/2008/04/28/load-balancer-update/). Most places run a dedicated hardward loadbalancers from F5 or Cisco or Juniper.