Here are some ping pong balls hanging up in the liquor section spotted at a local grocery store in San Diego, August 2010. The most common usage for ping pong balls other than for a table game back in 1957 is for playing Beer Pong, a fun, stupid and sometimes ill-advised game that promotes over-imbibing of beer. Now, the store itself isn't directly promoting drinking games as it is an outside vendor who hangs up the racks of various impulse buy items. It is more than likely that the store is unaware the balls are in the liquor department.
These packs are not hanging up over the beer (yet) but they are in the general alcohol section. I have no doubt the store would not hesitate to move the balls to the toy section if brought to their attention.