Dynamic load
Where cloud excels is if you have a dynamic or cyclic load - so you can spin up 500 nodes to process a sudden influx of workload, and then throw all but two of them away for the remainder of the day/month/year . Think the Wimbledon or Superbowl web servers for example. Where it sucks (financially, at least) is when you have a constant baseload of work, where you end up paying a flexibility premium for a service that is running at constant load 24/7 .