Drupal Hosted on Google
Today it was announced that the Google App Engine (GAE) will support PHP. This means that sites built on platforms such as Drupal or Wordpress can be hosted within the massive Google infrastructure. The GAE can support websites and applications that grow from one to millions of users without some of the problems normally associated with server backend infrastructure.
So? GAE charges by CPU usage instead of instance hours so, for sites with low traffic, hosting can be much cheaper. And if your site suddenly gets hits from lots of users, the load is spread across the Google's vast vast computing cloud so your users still get their pages served quickly. Google isn't the first to sell off spare capacity in its infrastructure, Amazon have been successfully doing this for some years with its Elastic Compute Cloud (EC2) service.
The only current problem is that GAE is not quite an out-of-the-box solution for Drupal: if that's what you want then companies such as Acquia or Pantheon can help. However, there's an excellent tutorial on installing Drupal on GAE at Boombatower.