It looks like Facebook is keeping our data longer than previously thought: deleted images aren't really gone, according to Ars Technica, and chat history can no longer be deleted, according to All Facebook. If Facebook was a small service, this would be a minor annoyance, but with some 500 million users, the problem is much more significant.
Facebook is struggling with deleting user photos: if you know the URL of the image, you can still access it. The issue came to light more than a year ago when Facebook was discovered as one of the worst social networks for deleting uploading pictures. The photos are still on Facebook's content delivery network (CDN) servers, despite being deleted one or two years ago, and you can still access them if you save the direct link to the image before deleting. "We're currently working with the CDN on a fix that will delete photo and video content from the CDN's cache shortly after it's removed on Facebook," a Facebook spokesperson told Ars. "The fix is already in place for videos, and we hope to implement it for profile pictures and photos in the coming weeks."
At the same time, users trying to delete their Facebook chats will have to find another IM program, because they can no longer erase their chat history. There's already a thread on Facebook with over 100 posts complaining about the removal of the feature. A "Clear Chat History" link used to be under the thumbnail of your profile picture in the chat box, and has been there since Facebook launched its chat program in April 2008. The feature was apparently removed with a recent chat upgrade, there's no telling whether it will come back, and there's no option to avoid having your chat history displayed.