The fare inspectors do not always give you a warning. I got on a Viva Pink a few weeks ago and sat opposite a man talking to the fare inspectors. When I showed the fare inspectors my ticket they showed my validated ticket to the man and explained to him what the tickets looked like and that it was good for a certain amount of time. There followed an embarrassing period of whining and complaining by the man as the fare inspector explained how was about to part with a good chunk of his money. This wasn't terribly unusual, I've seen the scene play out many times in Ottawa, but what struck me was his chief argument, namely "I didn't know you had to pay because nobody ever checked my ticket".
I wonder if that was the best excuse he could think up on the spot, or if some people really do believe that the service is free. During the discussion between this man and the fare inspector there was no indication that he had been caught before. I think $155 is sufficient or possible too high for the first infraction, but the fine should certainly go up for ever subsequent infraction and there should be more signs indicating the fine for not having a ticket.