robzilla - 6:28 pm on Mar 31, 2012 (gmt 0)

Here's what I read over at Amazon CloudFront: [aws.amazon.com...]

Streaming has several potential benefits for you and your end users. Streaming can provide more flexibility in playback: with streaming, it’s easy to pause, rewind, and fast-forward a media file to whatever spot is needed, without needing to worry about how much of the file has already been downloaded to the browser. You can also configure your streaming distributions to use dynamic bit-rate streaming. When enabled, this feature lets you store multiple copies of the same video, each encoded at different quality levels. Your distribution will then automatically adjust the quality of your video based on the speed of the end user’s internet connection. Streaming also can give you more control over your content, as no file remains on the end-user’s computer when they finish watching a video. Additionally, streaming can save you money, as it only delivers portions of a media file that the end-users actually watch. In contrast, with traditional downloads, frequently the whole media file will be downloaded by the end-users, even if they only watch a portion of the file.

You're right in saying that it's not necessary to download the whole file before playback can begin, I misremembered or misinterpreted that from the above text.