I like seeing more and more uses of prototype. I'm not sure if the big guys will win out with their UI toolkits (Yahoo UI/GWT) or if it will always feel better to put things together by hand. Either way it is good to understand how this stuff works. This is an edit in place example that is similar to what you see on flickr.
I've seen something like this a number of times when I've visited sites. They want your feedback on something or other while you are browsing. It is a little floating plus feedback sign that hangs out in the lower right hand corner. Check it out.