I seemeth to me that if at a wedding - at least at the reception - you have a camera on a normal height tripod, one rule applies: People will aways walk in front of it! I guess a variation of Murphy's law.

I have tripods that with a bit of fiddling can get cameras up to about 2.1m. At the wedding filmed last Saturday, I used the extensions in the church and did not get one shot obstructed. But then, forgetting the lessons learnt one other time, I chose not to use them at the reception and regretted it from about 3 minutes after the show started rolling! Never again.

no - it's the bride and groom rule - at a wedding attention will tend to cluster around the b&g.

to prove that there is no tripod rule:

Point your camera at a corner of the room that the B&g don't intend to visit leave it on the tripod for an hour or two. Check the tape - no obstructions!

QED