My father-in-law worked in graphic arts research at R. I. T. In the late eighties he developed a dog and pony show to show printers and packagers how to design and print bar codes that would scan. That's more tricky than you might think. For instance, if the paper absorbs the ink unevenly it makes a fuzzy line that confuses the scanner.
After some three or so years of hosting and traveling here and there all over the country they thought they had covered just about every one.
Then the phone rang.
"Can you tell me about bar codes?"
"Certainly. Who am I speaking with?"
"This is the California Distillers, Vintners and Brewers Association."
Boy. Did he enjoy those workshops? In the brewery--I mean the field?
Updated for clarity thanks to Roy's comment. 05/09/06