In Germany we are having a big issue with privacy and data protection issues. By some laws (e.g. Telemediengesetz) it is forbitten to provide user information for third party sites. Facebook was aimed like it always hits the largest players and website owners using the like button were sued.

Heise.de programmed now a solution which makes social sharing a bit more comlicated but safe by German law.

If you want to use it for your site go on
www.heise.de/extras/socialshareprivacy