@Thomas,
Thomas wrote:The foreign countries you mention solve this problem by requiring everyone---citizen or not---to carry a photo ID.
That's not true for Germany (see my above posts) - for German citizens as well as for foreigners.
(Non-Schengen country citizen, though, must have the border papers still within a 30-km-zone of the border - since they are the only persons whose papers can be controlled when enterying Germany.)
Foreigner or German citizen - you must own some ID-papers but are not forced to carry them with you. (Though for non-EU-/non-Schengen-country persons it would fasten the procedure a lot if they are asked for papers and had them at hand.
)