Well, it hasn't happened yet, but there's already been so much drama around this one!
Wedding is the end of May. My friend and his lovely fiancée have had nearly nothing but grief from her parents over the last few months. This includes:
-- having to move the wedding reception venue because MIL2B insisted that it wasn't close enough to where she and FIL2B live (although my friend and his DF had got a good price and a lovely venue and it wasn't much further than the new venue)
-- the new reception venue is more expensive, and as PIL2B are paying for it, they wanted to have a "tea party" theme i.e. no alcohol and lots of little cakes. This nearly caused a total bust-up between my friend's parents and PIL2B because...
-- my friend's parents (once they stopped laughing at the idea of a wedding in their family involving ZERO BOOZE) have paid for a free bar so we can all have a knees-up in the evening, which is what both bride and groom and all their friends want. This has obviously put PIL2B noses out of joint (they're now barely on speaking terms with my friend's parents) because THEY wanted a tea party (and don't give a toss what their daughter, the bride, wants)
-- because the venue is more expensive, us guests must now all pay £4 transport to get to the reception from the venue, and we had to include this with our RSVP
-- when my friend's mother said DF's ideas for her dress were lovely, poor DF said "well, I guess it's not going to be my decision in the end" 
-- PIL2B insisted on writing and sending all the invitations out and they spelt my name wrong [clutches pearls] AND used the full, formal version of it, which I loathe and detest
I'm sure there's more that I've forgotten about!!!