Your law may not be properly upheld in practice but that does not change the situation of Germany being in the very small club of countries where the art of street photography is effectively illegal or at least very cumbersome.
Yes, and they keep constantly weeping about all the street photography they miss out. Well, actually, they don't. It seems they like their law like that. For some reason, people assume that street photography, or being able to shoot photos of whoever you want, is a right nobody would object to. Well, I do, especially in times of facebook, and it seems I am not alone.
Things like google glass belong, as far as I am concerned, banned, and its use in public places punishable by jail. In the same vein, cell phones should be forbidden from having a camera.
There is this thing with privacy. For some reason, everybody is for it as long as it is not them who have to respect it.