Most of the time the player turns out to be wrong and is using the forum to strong arm a casino. I still always start off taking the player's side until the book proves him guilty.
For some of these accusations, the casinos in question are not on bitcointalk or their handlers have become inactive. What side do one take then. Well, I have heard of the dangers of a single story and while the player with the complaint may want to play to our sympathy, I always take the a neutral side. I do the best I can to provide the player with the necessary channels and resources to pass their complaint however, until I hear the side of the casino, I stay neutral.