I realized I was hijacking another post so I thought I'd move the comments over here.
An unplugged wedding is when the couple RESPECTFULLY requests that guests refrain from taking photos during either the ceremony, reception or both.
There are many reasons to do it and as long as you let guests know in advance it's usually not a problem. My photographer was so happy I did this and I've ever heard of some photogs offering discounts to couples who do it.
1- Camera flashes wash out pix if taken at the exact same moment as the professional's. The auto focus can also cause red or green lights on faces.
2- You'll end up with pictures of people taking pictures.
3- Some guests will be more focused on taking pix/video than paying attention and being present with you in that moment.
4- Some guests (there's usually always 1) fancy themselves photographers and have been known to stand in the aisle, on a pew, behind the Bride and Groom or even behind the officiant to get a shot.