Some people believe so, including my chiropractor....

Over-sized wallets, or carrying anything in a back pocket that makes it bulge out more than the other can lead to back problems due to the angle at which your hips settle when you sit.

 

CJ's wallet (l), JayCee's wallet (r). Notice which one has more money??

 

Carrying your wallet in your front pocket, in your man-purse, or using a 'slim' wallet, with an always-handy handkerchief in the opposite pocket can help alleviate those problems!!  (CAUTION:  Check gang signs/symbols in your area before choosing your handkerchief color.)  (I'm just kidding, you know.. unless the Krips in Kaplan are on the prowl again...)

 

(Via Neil Baum's Blog)