You mention travelling between countries in Europe without passports.
As you may know, Denmark is a non-Schengen country, and loves tootling its own horn. Especially yesterday (aaargh. Ex-commies and neo-nazis and stay-at-homes....ahem. Sorry)
I live 20 miles from the German border, and this means that I can't go and buy cheap beer without bringing my passport.
Now: we're talking cross the line, go 50 yds, park the car, buy the beer, load the car, drive 50 yds, cross the line, drive home.
The beer, by the way, is brewed within 100 miles of the border, trucked to Germany to a central logistics facility somewhere down south, trucked back to the border shops, picked up by thirsty Danes, and taken back to Denmark.
Where's the logic in that? I guess it's the same all over.
Have you tried tax-free shopping in Philly, btw?
rgds
Charlie Oscar X-ray