Why you might want to consider discouraging guests taking photos during the ceremony.
You’ve probably paid a lot of money for your photographer and videographer to film your wedding and get the best shots. The rest of the day is probably ok for me if they have free rein with their cameras but the ceremony is the most important event of the day, if not of your life and should be respected as such.
I’ve only once had any negative feedback from a bride and it was about the flashes that appeared on the video during the ceremony. There was literally nothing I could do to remove the flashes from the film. I sent her a screenshot showing her who was responsible and in this case it showed her photographer and his assistant both with flash units mounted on their cameras standing near the back of the room.
The same could apply to your guests of course if you allow them to take photos. They may use the flash on their phones which is less likely to show up on my film than a professional flash of course but it might if they are in the frame of the shots I am filming.
If they start getting up out of their seats and moving around to take their photos then this only gets worse.
So all in all the photographer, myself and the registrar/celebrant all have an interest in the guests staying seated and not using their cameras during the ceremony.
At most weddings I have been to there will be an announcement at the start by the registrar, vicar or priest to the effect that no photography is allowed except by the professionals and thankfully at nearly every wedding I have ever been to this rule has been observed by the guests.
At a lot of weddings there is also a notice put up to this effect on entry to the hall so you might want to consider having that.
After the ceremony
Once the ceremony is over and the register has been signed then there is usually an announcement that the guests may now come to the front and take photographs which is fine by me. I quite enjoy capturing clips that show what the guest is seeing on the back of their phone as well as the view of you as a couple.
At the other extreme I was once asked to film a wedding where there were no rules. In fact the guests didn't know they were going to a wedding until there was an announcement. They thought they were invited to an engagement party and had dressed accordingly. Even the brides father didn't know he was at a wedding until he was asked by the bride in the bar area to give her away with me filming his reaction. Thankfully he agreed and the ceremony continued after the announcement with the guests all gathered around in a huddle like they were partying with everyone filming on their phones, flashes going and me trying to keep my camera steady amongst them! The resulting film was exactly what the couple wanted and everyone had a great time.