I think everybody allready knows: StudiVZ the popular german student network is selling the contact information of it’s users to other companies.
A funny example hit me last week. When I opened my e-mail I got a limited invitation to a new service / obviously spam. When I checked the disclaimer I found that the startup is located in Leipzig, Germany where my father is advocate I forwarded the mail to him and he checked it. It seems that the guy who founded the startup is alumnii of Handelshochschule Leipzig a production facility for highly qualified management personel (a lot of internet startups originated there e.g. Spreadshirts). From contacts within HHL I heard that all the contact information aquired by this new startup originted from StudiVZ.
My father informed me that it is german law that you have to protect yout email address. So if you sign up at a social network and wondering that you get strange invitations it’s your fault and there is nothing what you can to about it but modify you spamfilter.
I think in this grey area there is a lot of work to be done for personal privacy. Politicians are talking about storing your connection data (Vorratsdatenspeicherung) to find Terrorists. But I think the protection of individual privacy is more important that to hunt a ghost.