Fools! A lot of people knew that trick. Very easy to smuggle beverages in that way. And, it doesn't have to be beer. Heck, I've known people to smuggle in plain water that way. (i.e. Warped Tour concert - 10 hours outside in the heat and sun. Venue wanted $5 per bottle of water.)
My favorite smuggling of beverages: Buffalo Bills vs. Redskins game at Rich Stadium. My brother (big guy) had slightly baggy jeans on. 12 cans in each pant leg. He smuggled in a case of beer. How? It's crowded at the gate, security is in a hurry, he had a beer in his hand. "I'll take that" "Hey, just let me finish it, there's another in my coat pocket, you can have that one." Security with a smug look on his face grabbed the beer from his pocket as he finished chugging the beer in his hand, then handed the empty to the security guy. Security guy's hands are full, he's satisfied he caught someone trying to smuggle in a can of beer, brother just waddled in with the case of beer in his pants legs. He had to walk slow til he got to our section, but once he got to our seats, he gave out about 12 of the beers to people around us and kept a 6 for each of us.