I had a dentist once ask me to sign a form that I agreed to pay a penalty of $50.00 if I kept the dentist waiting. Really? A patient making the dentist wait? So I said I would be happy to sign it, IF he was willing to do the same for me. The receptionist looked as me like I was crazy. So told her my time was just as valuable as his and since I had to take off time from work, drive to the appointment only to be kept waiting it would make sense that I be compensated as he would like to be. The dentist said I didn't need to sign it, and he kept me as a patient.
It makes sense that a doctor really doesn't know what he is going to encounter when he walks into the exam room, but I do expect if they are running any more than 30 minutes behind that they tell me this when I check in. Because we all have more to do than sit and wait. I do take sewing or a book to entertain myself but it is totally rude not to warn us. We can always run an errand and come back. If I have an urgent need to see the Dr then they tell me what time to come in and so I am not taking up space in the waiting room.