There seems to be a certain protocol that has to be obeyed. To mix people up and have them sit at different tables just means that everyone mixes. This is surely better than each family and friends keeping to their own tables just because that is the most comfortable thing for them. I think it is really bad manners to move name cards and then sit where you like. A lot of planning would have gone into who sits where.
All this could be avoided if weddings were to consist of a buffet where everyone helps themselves, then you could stand up, sit down, or at the bar. Much more relaxed I think than the more formal sit down. But leave me out of it, I am with Bamhan and would much prefer to stay at home.