You put a file (i.e., content of some sort, for example, an image file) into S3, create a distribution that, you guessed it, distributes copies of that file from the originating S3 location, and then put links to the object in your web application using the distribution name. Amazon then arranges to move copies to its edge locations across the United States, Europe and Asia.

Easy-peasy, eh?

A lot of discussion about the service has, as you might expect, gone on in the blogosphere. One interesting posting by Dan Rayburn, Principal Analyst at Frost and Sullivan, is titled "Why Amazon's CDN Offering is No Threat to Akamai, Limelight or CDN Pricing." It's a pretty interesting piece and argues against those who, apparently, believe CloudFront will decimate the major CDN networks. Rayburn points out some reasons why CloudFront is no threat to the incumbents:

1. It doesn't have the reach they do: They have zillions of machines scattered around the globe located inside ISPs. By contrast Amazon has an unknown number of machines in a limited number of locations, all of which are Amazon data centers. Rayburn doesn't say this, but this means content retrieval requires an additional hop from the end users ISP to the Amazon location.

2. The incumbents aren't interested in the customers Amazon is targeting. The incumbents want customers who are ready to spend hundreds or thousands of dollars per month. It's not economically feasible for them to deal with a customer who might spend $100 or so per month.

3. At really large scale, Amazon's pricing is actually more expensive than the incumbents, who can offer big discounts for high usage.

Rayburn then points out that markets aren't homogenous; both Hyundai and BMW sell cars, but really don't compete.

He's right to dismiss the postings that posit CloudFront as a threat to Akamai or Limelight. Someone with huge content delivery needs that come from all over the world would find CloudFront inadequate, perhaps laughably so. However, I think he sells the impact of CloudFront short, relegating it to a Hyundai role (leaving aside the fact that many people purchase BMWs to send a message about their prosperity or self-regard, which is a less powerful motive in most business settings—not that many companies are going to be willing to spend significantly more just to tell people that they use Akamai).