Because if you tried it today you would be arrested for terrorism.

Well said. Let's not forget this from the last year: http://en.wikipedia.org/wiki/2007_Boston_bomb_scare

This one was good too - bomb squad called in over cardboard boxes painted like Mario ? blocks.

http://www.bladediary.com/questionblocks/index.html

Don't make excuses. The 1950s was a very conformist era, maybe they would have been arrested for being communists.

And they didn't even have Home Depot, Kinko's, GPS or Arduinos. There are people who practically make a career out of such pranks, sometimes much less benign -- Billboard Liberation Front, for example.

http://www.billboardliberation.com/2008/02/28/video-of-the-a...