Wedding reception mistakes made by others that you learned from

I'd like to know what are some disasters or mistakes that you've seen at other weddings that will help you avoid calamity on your big day? I recently went to a wedding that was held on Wednesday at 4pm and practically no one showed up. I've also been to a reception where there was no dancing for guests. The B&G was late in arriving then they had the first dance, bride/dad, groom/mom and dinner. Then there was the bridal party dance. Then the cake was cut and they started the money dance which went on for far, far, FAR too many songs. Then the bouquet and the final song and done.

There wasn't ONE single time where the guests could get up and dance. I don't think it was intentional I think it was a matter of timing with everything.

Another-
I went to another wedding where the guest list was HUGE (nearly 400) and the reception was held in a park. The food was at different stations (all heavy appetizers). Not only wasn't there enough food for the guests but there weren't enough plates or silverware and NO ONE was monitoring to make sure that the guests were actual guests, and not just people hanging out at the park who helped themselves to the food and open bar.

Another-
A friend of mine went to a wedding recently where there wasn't a single thing she could eat (she's a vegetarian). The salad had bacon in it (or maybe the dressing did and the salad was already dressed). The mac & cheese had ham, the veggies were cooked in bacon fat and had bacon. She said it was a bacon lovers feast and her husband loved it but they left early because she was starving.

My final one-
Some friends of mine got married at a winery and while they were allowed to serve whatever hard liquor they wanted the HAD to use the winery's wine. The winery would bill them for however much they used. They hired bartenders from a local chain restaurant near their house. What they SHOULD have done is somehow kept track of how much alcohol they had and how much was used but they didn't. Somehow ALL the hard liquor disappeared by the end of the night (and we know it wasn't all drunk by guests) and the winery said they went through a stupid amount of wine. It would have equaled EACH guest drinking 2 bottles of wine which would NOT have happened when there was top shelf liquor to be drunk instead of pretty crappy wine. But they had no way to contest it so they had to pay for it and they weren't able to return all the unused hard liquor because it disappeared.

I'm interested to hear about your experiences.