I made a reservation through Holiday Inn's website last fall for a convention this summer and received a confirmation e-mail. I found out a few weeks ago that the hotel canceled my reservation and did not inform me, either by phone or e-mail.
I only found out now by happening to call to confirm. It would have been bad to show up and only be told then that they decided to cancel my reservation without telling me. The hotel staff was rude and didn't even call to explain when they said that they would. I would never make a reservation with a hotel that may decide at any time to cancel it and not tell me.