Originally Posted by k0nr4d

Imagine you have a 10mbyte video file that is 3 minutes long and a guy on a 10mbit connection. For the sake of simplicity, lets say he can download at 1mbyte/second. This is slightly inaccurate but I don't feel like busting out the proper math . Not ever user watches every second of every video they watch.

Via http, this guy loads up this video on your site and it downloads in approximately 10 seconds. While it's three minutes long, he might decide to go watch another video instead after 15 seconds. He's downloaded 3 minutes of video but watched 15 seconds of it.

Via RTMP, this guy loads up this video on your site and it's "real streaming". If he watches 15 seconds of it, he downloads more or less 15 seconds of it.

So in a nutshell, with rtmp you waste less bandwidth. The http problem can be mitigated by throttling each user connection to just over the amount of kbytes/sec it takes to stream the video without stopping to buffer all the time, but in the real world on say a tube site you have tons of varying bitrates so there's no good way to optimize this.