From Wikipedia
In the history of Major League Baseball, six players have been issued intentional walks with the bases loaded (thus giving the batting team an automatic run). This is similar to the intentional safety in American football, which also concedes a certain amount of points to the opposing team in order to avoid a situation in which the opposing team might score more points than the safety itself. This is only done in the rarest of cases, typically when the pitching team is leading by four runs or less late in the game and a particularly feared hitter is at the plate. The six players given such passes are Abner Dalrymple (1881), Nap Lajoie (1901), Del Bissonette (1928), Bill Nicholson (1944), Barry Bonds (1998), and Josh Hamilton (2008). In all six cases, the pitching team went on to win the game.[4][5]
If this is correct, walking a hitter with the bases loaded has worked everytime. Small sampling, but still 6 for 6! Those are the numbers!
Every time a pitcher has thrown 12 perfect innings in a game, his team has lost! The numbers don't lie, throwing 12 perfect innings in a game is bad for your team!