Ken Varnum (RSS4lib) draws some parallels between RSS and shipping containers.
"In a nutshell, the standardized shipping container revolutionized international trade by vastly speeding up the loading and unloading of ships... RSS is the box into which any old thing can be packed, for uniform shipping from producer to consumer. A paragraph of text, an audio podcast, a video podcast, a Word document... " -- RSS: The Shipping Container of the Internet
I'm thinking that the feed is like a freighter and RSS items (posts) are the containers. I like the analogy, but freighters are discrete, whereas a feed is a stream of containers, that can theoretically keep on arriving at the port until the harbour master screams "cargo overload" and unsubscribes. :-)