A thread on OwnedCore alleges that World of Warcraft screenshots are now being automatically watermarked with account-identifying information inside, and offers steps for you to see this information for yourself.
Sharpening images to high levels reveals non-random, non-artificated sets of repeating symbols which some users have discovered to contain references to player account names, realm time, and realm IP address.
The pattern does not contain any information such as passwords, user IPs or real names, but users have raised concerns that this is not mentioned in the game’s Terms of Service agreement and that Blizzard should have disclosed it. The popular theory at the moment is that the functionality was added in order to track any possible leaks from NDA’d alpha testers, but testing has shown that this has been in place some time between 2008 and 2010.
Blizzard have yet to release an official comment.