Should wedding photographers have two cameras?

Photographers choice, as long as you have great photos, this is nothing you need to be concerned with. Good experienced, photographers will look after that stuff. 

Absolutely we do a number of things as professional photographers to make sure that your images of kept safe and that if we have a failure of one camera we quickly have another camera on your shoulder ready so we missed none of the action. There is none of this asking the Wedding to stop well we go get another one from the car. We also have multiple memory cards in each camera so your photos are doubly safe each time they are taken they are backed up immediately.

Every camera has a number of lenses in case there is a failure of those as well so we have back up so we are back ups.

Absolutely! No doubt about it. And for that matter, multiple lenses, multiple flash's and camera's that record to 2 cards. Technology as we know can fail and camera's can reach the end of life without warning. I've had lenses fail on me at weddings - however it did not affect me doing the job, because of backups. I even go as far as 3 camera bodies because I like to shoot the wedding with 2 camera's at all times. 

YES! As a professional photographer & videographer, I have two camera bodies on me at all times. This allows us to not only use different lenses for a variety of looks, but to have a back up in case (heaven forbid) anything goes wrong with one.

Absolutely - I have had a few occasions where for some reason or another, my camera failed to operate - this is very annoying and embarassing

I now have two brand new camera bodies

I have multiple batteries, all charged in readiness for the day

Not only that, I have numberous SDcards, I do regular back-ups during the day

In addition, I have duplicate speedlights and strobes

Basically, I have two of everything in case one gives up for whatever reason

No they should have 3 or at least 2 plus a spare one in the car if they do not have an assistant to hold them.

Yes. Not only for reassurance for a camera not functioning but helps with time, not having to change lenses. It also means you can catch off guard moments that can't be planned for.

I use two cameras as it means I can cover a better range of focal length from wide angle to quite tight. But a single camera and lens can be just as effective so it depends a lot on the shooting style of the photographer.

A similar question would be "should a photographer always have a backup camera?" The answer is yes! Cameras and lenses can fail and you can never know when, so back up gear is essential.

I can see the unanimous response below is yes & I 100% agree!

It's important not only as a backup to your primary camera but also ads versitility to your service offering. For couples that are not utilising a videographer the second camera can be a perfect tool to quickly set up on a trip to capture some B-Roll or simply record the ceremony. While your role as the photographer remains the most important part of your offering added flexibility with basic videography can go a long way when discussing & delivering your services with clients.

I shoot weddings with my Canon 5Ds & use my Canon 80D as my back up/secondary camera. 

Yes, I always have 2 cameras for wedding and all other comercial photo shoot. For wedding jobs, most of our package design as 2 photographers, each photographer has 2 camers, this is not just a back up, the client will have much more photos with different angles and aspects.