Technology journalist Glenn Fleishman, who writes the Practical Mac column in our pages, has a cogent analysis of Amazon.com's new EC2 service in the comments, and calls it another piece in the puzzle for wide availability of on-demand commodity computing.

Here's what else Amazon needs to complete the puzzle, he writes:

--Per CPU hour or per transaction SQL service, with the database storage persistent and charged at S3 storage rates.

--Persistent hard drive images that can be mounted and written within the EC2 system. Right now, you create an entire disk image that is non-persistent. If it crashes or when you shut it down, all data on the virtual hard drives is dumped.

--Automatic load balancing for incoming requests across a set of instances. This would allow me to go from, say, 10 virtual servers feeding out my Web site to 1,000 without having to build the software that takes requests to my Web address and redirects that.

"This marks another step in Amazon trying to develop another multi-billion-dollar line of revenue," he writes. "I wouldn't say that they will develop that much out of it, but there's a large potential to make huge sums from tiny amounts."