At last month's huge U2 show at the Rose Bowl in Pasadena, Calif., how could you tell the difference between the professional photographers and your average amateurs?
Answer: the professionals were the ones whisked away after Bono and friends finished their third song, and the amateurs were still there, happily shooting to their heart's content.
As the article points out, with everyone carrying cell phones with cameras, and the increasing quality and resolution of small cameras, it's both getting harder and harder to stop people from taking pictures, and the line between professional and amateur is getting smaller and smaller.
I remember several years ago going to a concert at Radio City Music Hall where they made people check in their cameras. At the end of the show, we all lined up while they tried to find each persons camera; which took a long time as they had the couple of hundred cameras randomly placed on two tables and they had to basically look at each one to see if it had the right claim number on it. It may have been less annoying if there still hadn't been dozen's of people taking pictures throughout the show. Ahh, happy times.