As of now it seems that this is just scam in the case of bitcoin.de. This is not the first attempt of this kind. The person trying to make money out of this wasn't able to provide any proof that this data is indeed what he claims it is.
Best regards
Oliver
This is good to know, it would be good to hear from the other sites, though I suspect this is a hoax/scam. As others have noted freebitco.in has a lot of users, but I'm not sure what the value of the passwords would be since they are tied to btc addresses not anything useful.
Well, you can change receiving address but then user would get email about that. Only way it could work is if rhat mail went to spam folder. Also problem is that users have same passwords for many sites, so somebody could hack much more things then just freebitco.in account.
The bitcoin stored on sites like freebitco.in are likely little to none and it would likely not even be worth it to attempt to steal funds from these accounts. There may be a very small number of accounts that have something "writing home about" but the overall take would be very little.