I use the one-line URL embedding to display images hosted on Flickr via my WordPress blogs, via the oEmbed framework. However, it seems that the HTML which actually links to the image at Flickr is only ever generated when a routine like wp_update_post() is called. This creates a problem. If I ever re-upload the image (after additional post-processing) or change the metadata associated with it via a 3rd party application (I'm using Adobe Lightroom and Jeffrey Friedl's Flickr plugin) then the image URLs at Flickr are re-generated, even though he URL which is used to refer to the image at Flickr is not. This results in all the altered photos becoming "This photo not found at Flickr" placeholders in older blog posts, even though the click-through link still works. If I edit the post and click "update" without changing anything, then the oEmbed code runs again, and I get a new, valid URL for the image, and the post looks fine.
It would be nice if there were an option to schedule a daily "oEmbed update" run or something, where any post containing oEmbed triggering text were automatically updated to reflect the most recent image URLs at Flickr. I wouldn't be surprised if there are similar issues with other oEmbed providers, where some of the information that's retrieved during the oEmbed dialog actually isn't permanent, and might need to be updated later.
I can create a plugin to fix this locally, but anybody else who happens to use my Creative Commons licensed images in their WP blogs will have the same problem.