[Kudos]

Tumblr and Twitter both used to, and I've met a bunch of developers at meetups who rather than think S3 is a CDN, do not understand what a CDN is.

[kalleboo]

Using S3 for file hosting is still a better solution than using a raw box (or shared virtual hosting) which is what most people who use S3 instead of a CDN would have been doing otherwise.