Yes, I'm very sure about this and it's only getting worse these days for travel between Netherlands and Germany. Especially when you cross the border in the southern part of the country.

I have never - ever - had a passport check on trains within the Benelux/France/Germany region, including Thalys. I have lived in Brussels and clocked up a fair number of trans-border journeys. The ticket checks are much more likely.

Spot checks on ID cards/passports do exist, but these are supposed to be few and far between, or when there is a big event on, or when they have information suggesting people will be using the train to travel illegally.

I have once been stopped by plain clothes French customs officers at Paris Gare du Nord getting on a train to BRU - the check was extremely cursory. Again, this was a spot check and the general rule is that you will never get stopped at all.

I remember when I took that train in Apr 2004 with my mate the border guards chatted with us both ways but didn't want to see any ID. The Germans wanted us to point out our bags too but didn't look inside. It could have been because we both looked like we hadn't been in Amsterdam to soak up the culture.;)

I have lived on the border of France and Italy and would cross the border every day by train but ID check may have been only 10% of the time. On saturday I was at the CDG airport TGV station and was even stopped by a trio of customs agent + national police + intelligence in plain clothes :D They asked many questions but they never asked me where I was coming from, which I found very odd.

NOt to cry foul about "racial profiling" but this past summer while waiting on a train at the station in Cologne on my way to Amsterdam, an "undercover" passport control person asked to see my passport, I just showed him the cover which had the big old USA eagle on it, and that was fine, he didn't ask me to open it up. Then he went and asked another Black male on the platform, who didn't have an USA passport and hassled him a bit..