I'm not sure to what extend courts are going to judge to which jurisdiction a website belongs but I think most websites owned by German citizens count.

How would they know?

Because you weren't careful about separating your identities. Any competitor can ask a lawyer to send you a cease and desist letter to comply with law of having a proper impressum and that lawyer can bill you for sending that letter.

The German wikipedia does provide a summary: http://de.wikipedia.org/wiki/Impressumspflicht