Dave Winer has some comments about Flickr's use of RSS:

I know I'm the last person to discover how clever Flickr's RSS is. Here's the story. People were adding me as a contact as I kept uploading folders of pictures from my backlog. I would get an email every time it happened. I wondered why. I wonder no more. I started adding them as my own contacts, slowly, a few days ago. Cool, when I'd go to my Flickr contacts page, I could see if Betsy or Rex, Tara or Stewart had uploaded some new pics. Excellent. Then yesterday I wondered if they had an RSS feed for this. Yes, of course they do. Bing. I subscribed. Now, happily every time one of my contacts puts up a new picture, it shows up in my River of News and gets hooked on my fishing pole. Now every time I add a contact it's like subscribing in RSS. Scratch that, it's not "like" that at all. It's exactly that. Excellent.

From Scripting News: 12/13/2005
Referenced Tue Dec 13 2005 10:28:37 GMT-0700 (MST)

Two things caught my attention. First, not that "subscribing" isn't always about cutting and pasting RSS URLs into an aggregator. Dave used a Web-based application to "subscribe" to the new pictures from his contacts. RSS is just the delivery mechanism for getting that stream of data to the place where he pays attention.

Second, the metaphor of "rivers of news" and getting "caught" on Dave's fishing pole are ones I've used before in presentations and articles. I think it describes the reason why RSS is important and why using it is an adjustment for some people. They think of the Web as a collection of places to go visit rather than as streams of information to stand in and enjoy.