ok - and just what is so dangerous about this information? whatever can it be used for? do blizz brainwash and tag the players? will it leave players open for all sorts of identity theft? will it make it possible for you to steal my account from looking at my screenshots?

Interesting? Sure.
Relevant? Nah.

Well I am no expert on the topic nor have got included in finding it so I will just quote the forum that all the work is done:
"The secret watermark which is being intentionally embedded inside WoW generated screenshots below top quality, DOES NOT CONTAIN the account password, the IP address of the user or any personal information like name/surname etc. It does contain the account ID, a timestamp and the IP address of the current realm. It can be used by malicious hackers to link alt. characters to accounts and target specific spam or scam attacks"

and second concern is:
"But we found account and realm information which means that its aim is to secretly track the users, in addition to the known tracking methods that we agree to in the ToS."

and third concern which is no longer valid:
"Bear in mind that when this started, back in 2007, we were still using our account name to login so, before the battle.net conversion in 2009, the watermarks actually had really sensitive information... Between May 22, 2007 and November 11, 2009, any malicious hacker who knew about this could have used a screenshot of a lucrative character to find their actual username & active realm and then either try to scam them out of their password, or just brute-force it."

so I agree the information maybe is not as dangerous as it was before from the info these guys posted.

What do you mean by account ID?

An actual ID? - #34750473734?
WoW account name? - WOW1, WOW2, YOURWOWACCOUNTNAME?
Battle.net account name? - example@example.com?
Battle Tag name? Elenarie#2772?

that's fine. just remember there is healthy paranoia and unhealthy paranoia - this one was steering a bit close to tin foil hat territory. a critical approach to sources is always a good idea.

I believe its the actual ID i.e #34750473734?

Well, before the new Battle.net, those IDs were identical with your user name. So would-be hackers would have access to half of the information needed to log in to your account.

Also, with the presence of the server IP, it would be straightforward to find your realm. From there, one could attempt to scam you out of your password.

It's really puzzling to me why this is present in the pictures. What on earth could Blizzard possibly want with this? it seems like such an overkill way of exposing illegal server hosts when you lay your entire user base bare to scamming attacks.