Social media policies for weddings... Ott or understandable?

Understandable.

Like, just as an example here, with my own wedding. I didn't actually care if people posted stuff on social media, but there were pictures of my ceremony on Facebook before we were even halfway down the aisle after being announced as husband and wife. That's how quick some people are with this stuff, and I can understand why it would be upsetting to some people if there were more folks worried about putting things online than actually paying attention to the wedding.

A sign at the entrance to the venue, and having the officiant make some sort of announcement after guests arrive but before anyone walks down the aisle wouldn't be out of line.

People take pictures at weddings. People post some of the pictures they take. That's how it works. Get with the times. You don't own people's right to communicate. If you don't want photos of your wedding posted, then don't invite anyone to your wedding.

How rude and presumptuous to have policies at a wedding. Are you going to post the policies on the invitation so everyone knows what they're signing up for if they accept your invitation? Are you going to have people sign off on the policies with their RSVP? Who's gong to police the policies? What are you going to do if someone violates a policy--evict them from the venue? Honestly...

I don't think it is unreasonable to ask your guests to respect your excitement and refrain from sharing photos of your day before you have had the opportunity to, esp. with family members and friends unable to make it (pity that people aren't a bit more thoughtful and then it wouldn't need to be said). However, maybe you could set up an area with photo frames, chalkboard and chalk/whiteboard and markers for messages, and fun prop bits and pieces etc. that is in a corner or some similar background like a wall and ask that if they want to share photos of themselves at the wedding, to do it over there - that way they they can share their excitement and what they are wearing etc. without 'sharing' the things you would rather they don't. Good luck.

Depends on the exact policy. If the aim is to keep the ceremony and reception off of social media entirely, for the sake of privacy, or out of consideration for those who weren't invited, I think it's laudable.

No shots of behinds

No shots of behinds

IF they have cameras, they will take pictures. You can request that no one bring cameras.