Wedding photographers have received a lot of bad press recently, some of it justified, especially where the photographer took 96 images of the bridesmaids and only 11 of the groom! Plus the one where the photographer left a fire extinguisher in the shots when it would have been easy to remove it. In some of the incidents, it begs the question, how much did the couple pay for their photographer.
I will always ask you to provide a list of your "must have" images and will use either the best man or chief bridesmaid/matron of honour to go through the list to make sure that everyone on the list is included in the final photographs. After all, if you are paying a lot of money, you don't just want photographs of the bridesmaids or fire extiguishers!
I recommend you don't choose your wedding photographer based on price alone or whether or not they use a particular brand of camera/lens and always ask to see samples of their work beforehand and insist on seeing their last full wedding. A professional photographer will always be happy to show you a full wedding and even just a few samples.
Of course, equipment can fail and for that reason, I carry backup equipment to cover any eventuality but in the case of total photographic failure beyond my control, you will always get a full refund or an opportunity for a re shoot if possible at no extra charge.