You ordered that fabulous designer wedding gown direct from the designer's studio in England. Unfortunately it's lost in transit.  The custom tux for your groom is in the same package.

Your responsible, mature, trustworthy Best Man can't find the wedding rings you gave him yesterday.  The last time he remembers seeing the ringbox was when he set it on the top of the car . . .

You've hired the best photographer in town.  When a guest accidentally spills a glass of wine on the photographer, unfortunately the memory card in the photographer's pocket gets soaked.  There go the photographs.

Some friends are helping you load your wedding gifts into the car after the reception.  One of thems slips on the steps.  Your friend is fine.  Unfortunately the Waterford crystal vase Uncle Colin sent isn't.
 
The Army wants your groom.  Right now.

The reception venue requires a liability policy just in case someone is injured or damages their property.  You'll probably need a liquor liabiilty policy too.