Six months later, and Flickr now supports annotations using JavaScript and CSS, so know I know it's really possible. And when I saw Dan Lyke's take on it, well … it was time to update the code a bit.
So between answering tech support tickets and waiting for a large
harddrive to finish fscking, I banged on the code for
this, and now all you have to do is mouse into the squares on the
image to see the notes.
Much better this time around.
I should note that this doesn't work in IE (like that's a problem). The problem is that IE's implementation of JavaScript isn't standard—it's not even in the ballpark, so after a few hours, I'm not even bothering with it.
You have been warned.