The question isn't whether every game is fixed but rather if some games are fixed or manipulated in some way. This wouldn't necessarily be for a guaranteed result, it could even just be tilting the playing field in the direction of one team or another. Previous precedents have occurred in baseball and other sports:
Obviously, match fixing is most often associated with gambling via control of players or officials. However, MLB and television networks would also have a huge financial interest in keeping the standings tight or favoring large market teams. For example, in the 2007 NBA betting scandal, NBA referee Tim Donaghy alleged that the NBA conspired to add a 7th game to the 2002 Western Conference Finals.
One way to help eliminate this problem would be to use "robot" umps for ball/strike calls.
What do you think, does this ever happen in baseball? What would it look like if it did happen?