If you count sub-domains on Alexa top domains here's a few big companies in there like iStockPhoto and Debenhams -

  discover.istockphoto.com
  store.xda-developers.com
  support.sharebeast.com
  finance.debenhams.com
  poy.tsn.ca
  m.nzherald.co.nz
  blog.telmex.com
  business.un.org
  coinad.com
  status.formstack.com
  indulgy.com
  all-that-is-interesting.com
  pbh2.com
  edoqs.com
  grandascent.com
  locations.paychex.com
  pagelines.com
  danjur.com
  mrmoneymustache.com

We've got some historical stats for them here but we only started tracking in January -

https://trends.builtwith.com/hosting/Digital-Ocean

Not sure if this is of any interest but this is where they are getting new customers from (from most to least)

  Linode
  Softlayer	
  Rackspace	
  Amazon	
  GoDaddy