title: Why are some websites spread across www2, www3 sub-domains whilst others manage scaling without it?
body: <p>I know it's to do with having a variety of load balancing servers, but why do some sites make use of differently named "www" sub domains (www2.somesite.com, www3.somesite.com etc) where as other can be perfectly massive without doing this - ie all traffic is to www.hugesite.com.</p>
  
  <p>Does it indicate certain architectural decisions / have a specific purpose?  Can it be avoided or is it a limitation of having the site scale a certain way?</p>