I think Refs are the ones that fix games most of the time. I don't think they fix games much anymore. I think in the past years, like 4 years ago and back, right before Tim Donaghy or w/e his name is the ref that went to jail. I think they fix 2nd halfs, over/unders, as well. He admitted a couple of the big series like Kings vs Lakers was fixed for the Lakers to win. He said he isn't the only Ref that did it. I remember TNT use to always be DOGS during his years.
Sometimes its the trends that REFS like to call and not fixing the game. Some Refs call all fouls and possible fouls. Making the game more likely to go over, while stopping the clock to score. Whether some players/coaches are linked to it, I am not sure. But I think its highly unlikely players were in it to fix games, at least for majority of the games.
I have seen a lot of BS calls that favored a team and suddenly switch back and forth. And there are times it sticks with one team. Refs have the ability to change to momentum and possessions very easily. I believe players knew at times when the fix was in, for instance when Wade/Shaq won their first year together vs the Dallas Mavericks.
Wade got fouled, when never touched every time he drove in the game. He is going to continue to drive and attack the basket if he keeps getting calls but that doesn't mean he was part of the fix. Dallas literally was hitting a 3 pointer on every possession and Wade would come back at least getting a foul and mostly and ones back.
I use to gamble during this time, and there were refs that I use to see, that would warn me not to bet against the Dogs. They are usually easier to fix, with a point spread. I would see a lot of BS calls that these refs use to overturn with Charges/Offensive fouls, No calls, calls for one side and not the other, 3 second violations, fouls against players that would put certain players in foul trouble that make a big difference, and any grey area awards one team.
I believe most games aren't fix now days, but it was really bad during the Donaghy era for lots of years. After he got arrested, it just certified my beliefs with his words.