Web images to get expiration date
Found on BBC News on Monday, 24 January 2011

German researchers have created software called X-Pire that gives images an expiration date by tagging them with an encrypted key.
Dr Backes said development work began about 18 months ago as potentially risky patterns of activity on social networks, such as Facebook, showed a pressing need for such a system.
Viewing these images requires the free X-Pire browser add-on. Currently only a version that works with Firefox is available. Those without the viewer will be unable to see any protected image.
If you read through their FAQ, you will notice a nice little gem: "X-pire! offers no protection against the intentional copying of an image during the validity period (e.g. by taking a screnshot)". So, in other words, the team worked 1.5 years on an encoder that costs about $33 per year and a FireFox-only plugin which does not stop the user from taking a screenshot. Honestly, even if I could be bothered to install that plugin, the first thing to do is taking screenshots; especially because it is obvious that whoever put the picture online thinks it's embarrassing. Even if they disable screenshots one can simply use a virtual machine and grab the picture from the host system.