The Amazon EC2 Cloud is inexpensive, scalable, and you only pay for what you use. You can turn instances on or off at will which gives you extraordinary flexibility.

Each instance is the “equivalent of a system with a 1.7Ghz x86 processor, 1.75GB of RAM, 160GB of local disk, and 250Mb/s of network bandwidth.” To buy such a machine might cost $500 before hosting.

You can use an Amazon instance as a Web server or you can set up clusters of instances and use them for only short amounts of time to engage in heavy computing. To run a Web server would cost you about $75 per month plus any bandwidth that you use.

If you need a cluster of 100 machines for a short time for some kind of serious computing --say for one hour, it would cost you $10. So, you can leverage the equivalent of $50,000 worth of hardware for an hour for nearly nothing.

Sounds great, doesn't it? Unfortunately, it seems that the instances aren't 100% reliable and if an instance disappears for some reason, Amazon has no backup of it. We've experienced it at work. An instance we were using for client review just up and disappeared which meant having to create a new instance and rebuilding the site from our own repository. If you are looking at a site with lots of database driven content, like Drupal, this means importing that database.

What you gain in price can be lost in time. Time is worth money.

Lesson learned--don't use the cloud for anything mission critical. One blip and poof, your instance is hosed.