From snopes.com



   In his article "It Was a DeSoto," Louie W. Attebery writes about
   locating three articles that ran on in the Denver Post on
   consecutive days in 1960 and reported a story similar to the
   legend. In this case, a driver hired to deliver a load of concrete
   for a house addition grew irate after he waited for an hour and
   no one showed up at the home to take delivery. Suspecting that
   the owner was getting even with him for winning a $20 bet, the
   driver dumped his load of wet mix into the left rear window of
   the owner's DeSoto. The owner, in turn, claimed he had called
   the concrete company 90 minutes earlier and cancelled the
   order. Attebery notes, however, that the two men were friends,
   and that the whole incident might have been planned as a
   publicity stunt for the concrete company.

Drew Diaz