Recently, Caroline Wozniacki got into an extended argument with an umpire for the simple reason that the Danish player was not adequately familliar with the hindrance rules. Yesterday, Ana Ivanovic was surprised to have points docked when she was given a bathroom break after she served, and that break extended beyond the time allowed for leaving the court. Again, she was not familiar enough with the rules. In Ivanovic's case, I think she would have probably chosen to have the points docked, anyway, but the issue here is that she was so surprised to find that the score had changed.
There are a lot of rules in tennis, and--while the average player might be expected to experience confusion over some of them from time to time--it would seem that professional players would be able to recite them easily. (There are also fans who might consider checking the rules before they launch into diatribes about umpires. It is not an umpire's job to educate players on the rules of the game.)