An investigation of World of Warcraft’s print screen function has revealed that the screenshots outputted by World of Warcraft imprints an identifying watermark, which includes the account name, the server name and IP address.
The details are on the Ownedcore forums. Essentially if you take a screenshot of World of Warcraft with as little in the way of textures as possible (Sendatsu, the writer of the post, recommends glitching through the world in Dalaran in Crystalsong Forest), then set your screenshot quality to 9, before running the now white image through a sharpening filter a few times in any image editing software, things are going to start looking like this:
That bardcode includes detailed information of your account and realm information (no passwords are shared), along with the IP address of the server you’re playing on. Essentially, your anonymity is no longer protected by just blurring out your character name. There's no suggestion that passwords or accounts could be compromised via the details revealed.
We can speculate that the watermarks are included to track down anyone who infringes any NDA for upcoming releases, and to spot those playing on hacked or pirate servers. The question is; should this information be made public?
If you'd rather not be tagged, there are two options; either use a different way of taking screenshots, such as FRAPS or Steam's screenshot function, or set the screenshot quality to 10, which prevents the code from showing up.
We’ve reached out to Blizzard for comment, and will update you if and when we receive a statement.