I can think of at least three people that are kicking themselves right about now.
Hot flip-flops make cool million - Yahoo! Finance
In July 2009, man opened Flip Flop Shops inside Mandalay Bay Hotel & Casino in Las Vegas.
In August 2010, he passed the $1 million mark -- in part because flip-flops are hot.
NTTAWWT
"In the past three years, U.S. flip-flop sales have grown 8.2 percent. This accounts for $1.5 billion of U.S. surf-wear retail sales,"