The Milgram Experiment shows how people will do things under orders that they might otherwise think better of.
It might not be a good excuse, but "just taking orders" is a real effect.

Interesting that you mention "Happy Birthday". Copyright protection is the reason restaurant wait-staff crow some other tuneless "song" at you when they bring out the cake with the sparklers, instead of "Happy Birthday To You".

c.f http://www.snopes.com/music/songs/birthday.asp

While I agree with your fundamental position - technology in the last 10 years has brought massive challenges to the assumptions underlying the very nature of intellectual property - I find it ironic that you chose this example, since obviously someone still thinks the copyright in HappyBirthday is worth something.