@Emilie
I am afraid that most of the complaints would probably be to do with customer support.
I find that it is never really effective or fair when a company uses the people who are being complained about to handle complaints!
It should be a separate, dedicated department. Of course, they are not ever going to be completely impartial, seeing as they are working for the same company, but they are usually there to deal with issues that customer services has totally failed to deal with.
This is like saying, please call the employee that was rude to you to complain about someone being rude to you and expect them to make a judgement on it.