>However, streaming formats lose the bandwidth savings of HTTP caching, and
It's not "streaming formats" you mean here, but "streaming delivery protocols". In many cases the same file format can be used for both streaming and non-streaming delivery. In the case of QuickTime/MP4 and additional hint track is added to make the file streamable, but the audio/video format is unchanged.
There is a bandwidth downside to progressive download, as well. The browser may download the entire clip even though the user only watches the first couple of seconds, resulting in the vblogger paying for bandwidth that wasn't used to actually view video. (True streaming also lets you know exactly how much of your video was actually watched.)
On lossy links, progressive download will re-transmit dropped packets resulting in bandwidth charges at the server for retransmission.
>they spend more resources on persistent sockets and on memory for session
This depends upon the application, type of network, etc.
I'm not an advocate of streaming over non-streaming, but there are advantages and disadvantages to each and the issues can get rather complex. (The vBlog Central service is currently configured to only use progressive download, BTW.)
M. Sean Gilligan : 831-466-9788 x11
Catalla Systems, Inc.