Also had to show ID (passport, in my case, as a visitor from the US) to board planes in Europe.
While traveling on trains in Germany, I was also required to show ID.
Traveling on trains does not require an ID. You are not stopped randomly in Germany to show your ID. It never happened to me in the 40 years I am living in Estern Germany and Western Germany.
In Germany it is required that you own an ID (or Passport). But you are not required to have it on you.
That said, if police has a reason to identify you, because of suspicious behavior, police can have a hold of you until your identity is proven. That will happen when you are speeding for example.
Sometimes, suspicious behavior may be that your skin is not white enough.
1) "Have your passport on your person": Yes, unfortunately this country requires you to be able to provide some ID. No, you don't need to carry it with you. If you DON'T have one though, it might cause issues/trouble/cost money. [1] I assume the Germans were misinformed and scared, the anecdote was probably not true.
2) You have to show your ID or passport at the border (aka. the airport in this case). You don't need to do that if you move in the Schengen area: Travelling from Germany to the Netherlands won't require an ID. That said, maybe you talk about braindead boarding procedures only. Those exist. People like to make sure that you're the one that checked in and all and .. yeah.. Please provide your boarding pass and ID. Useless. Enforced randomly. Utterly insane. Consider it a nuisance if it happens, but .. it doesn't, most of the time.
3) You never need to show an ID in a train. Except: a) you cross a border and leave the Schengen area. Normal procedures, people will check your passport/ID b) you bought a ticket that says 'can be used in a train (as paper or digital), but requires an ID'. That's the DB (German Railway company) being insane, stupid, annoying, crap, (insert-more-expletives-here). You can buy a ticket at a counter and no one is ever going to ask you for your ID. And I guess no one knows why they consider it a reasonable thing to do for most online tickets/digital tickets.
So:
1) Wrong 2) Maybe 3) DB is run by idiots, is crap, sucks - and there is a workaround
1: Seems to be German only, Google translate? http://de.wikipedia.org/wiki/Personalausweisgesetz
This occurred on 21 July 2014, aboard IC 147, Amsterdam Centraal - Berlin Hbf.
At this point I am simply more amused by the number of people who've insisted that what happened, doesn't and can't happen, than I am annoyed by it.
That said: This particular border was/is monitored a bit more. Even cars crossing that border might get pulled over. Why? Certain harmless substances were/are (not sure about the current legislation) easier to get in the NL and people living close to the border tended to do shopping trips..
If this was a Schengen (inter-europe flight), the only reason you would need it would be on checkin if your airline checks this for revenue protection. By law there shouldn't be any passport checks (at least only randomly).
Anecdote: Travelled by airplane within Europe multiple times, never had to show my passport
>While traveling on trains in Germany, I was also required to show ID.
Which is only required if you get a non-transferrable online ticket. If you buy your ticket at the station, there is no need to show an ID on the train (in contrast to Amtrak)
That creates a problem because, obviously, the police is performing racial profiling and I met Caucasian or Black Japanese citizens who have been harassed by the police because they were not carrying any ID.
For the flight: Usually you either check in with your ID/passport in one way or another. That's true, I guess. As far as I'm aware at least, there's no way around it. They don't "check" you, but you prove that you booked your flight by presenting the ID. Bah.
For the hotels: That's the real issue. Ignore the rest. Most countries here seem to require that you give up your identity if you check into a hotel. The ID isn't always required - actually that's rare for me so far - but you're supposed to give up your name, private address and contact information. For .. random idiotic reasons I assume.
It's not the hotels that care here, though. Can't blame them.
Online checkin? Did multiple flights with Lufthansa, never had to show ID. Maybe depends on the airline