Thanks to Damien Broderick for sending me this link to a Washington Post story.
It seems that Germany has an obscure 1930s law that, with limited exemptions, prevents anyone using the title "Dr" unless they hold their doctorate or medical degree from a German university. Actually, the law was extended in 2001 to give the privilege to people with relevant degrees from other universities in the European Union. But if you are an academic from, say, the US or Australia, and you're working in Germany you will generally have to call yourself something like "Prof. Ian Thomas Baldwin, PhD, Cornell University". If you call yourself "Dr Baldwin", you will have committed a criminal offence. They take "title abuse" pretty seriously in the status-conscious land of the autobahn.
Well, here I am: almost through a second PhD for my mysterious reasons that I always find difficult to explain to people succinctly. I thought that one of the perks was that I could really revel in it next time I visit Germany, but obviously I was wrong.