Following the news of Sam Ruby's snapshot spec, here's my first pass at a newsfeed in the format that will not be known as Echo. This is, of course, a largely theoretical exercise, because, to my knowledge, there are no aggregators yet capable of reading the feed, but it was a nice excuse to get more up-close-and-personal with writing Blosxom flavours and to take a closer look at the spec.
If I can do it, then the fears that the format would be too complicated for vendors to support are pretty much shown to be unfounded, since I'm a freakin' lightweight. It took me about an hour looking at the spec and some sample feeds other people were generating to slap this together. No warranties express or implied, blah blah blah. Known bugs: I'm probably doing the wrong thing with the "modified" field for the entries.
The flavour files I came up with are here (zip file), and are released to the public domain. If you fix any bugs or make any improvements, let me know in the writebacks for this entry. Requires: Blosxom 2.0rc5 (might work with earlier versions, but it's untested), RSS10 plugin (yeah, you read that right -- I avoid reinventing many wheels by using this plugin), foreshortened plugin, lastmodified plugin.
edit: I checked the notEcho feed with a patched version of nntp/rss, and it works! Hooray for interop.
edit: The feed now validates. The updated flavour files require a small patch to the lastmodified plugin, I'm afraid. (included)
Fundamentally, there may be no basis for anything.