[tomcam]

I'm for this in principle, but I have absolutely no assurance that this is the number it's claimed to be. I would not like to be part of a vigilante attack on someone who turned out the wrong person.

[acqq]

See the photos from the streets. It's not "just a webpage" giving you the number.

http://hop3.de/litfass_en.html

Also in the German media (the phone number is in the text):

http://www.badische-zeitung.de/ausstellungen/kann-man-sich-n...

[anotheryou]

the exhibition space where the phone lies is well known, it's not a scam.