Timing is a big reason I don’t recommend an open mic at a wedding. If you have a lot of people come to speak, this can cause your guests to sit for too long. If you open a microphone up before dinner, it could take a while and the caterers won’t be able to time when to serve the meal.
Even if you do the open mic after dinner, the people may get antsy, causing them to look at their watches/phones and think about leaving early. It is better to keep your event moving. You want everyone to enjoy themselves – hopefully they stay and dance the night way! Here is a quote from a discussion about the open mic on The Knot from someone in the wedding party that exemplifies how an open mic can mess up the timing:
“At first it was fine, because I like listening to all the stories, but after awhile I was uber bored, but sat with a smile because I was at the head table. Then the last person said, “thanks for coming”, and everyone started to head out. I was like, WTF? I sat through so many people talking and I don’t even get to dance?…”