I think it's a good idea to have a phrase in the back of one's mind for times when someone, perhaps in all innocence and good intentions, assumes they'll be invited to your wedding.
I could totally see this happening with my family. If I ever were to get married, I think I would want a very, very small wedding, like a dozen people total. In my family it's traditional to have a big white wedding with all the extended family. So I could see people saying, when they hear about my (hypothetical, future) engagement, "Congratulations! When's the wedding? I can't wait to see it!" with big smiles and everything. And I think it would be good if I could immediately say, "Thank you! Not sure when yet, but I think it's going to be just a very small wedding," in kind of a tone that suggests they (and many other people) might not be invited.
Okay, this is basically the definition of 'borrowing trouble,' but I could completely see my dad casually giving out the date and location to people and inviting them to "come on over"--the more, the merrier. I would almost want to issue an edict that said, "If you did not receive an invitation from me or my partner directly, you are not invited, please do not attend. Invitations issued from my dad do not count!"
Of course I never would. But I can see how some people in similar circumstances would be tempted. Combine "going against tradition in this circle" with "casual communication" and you can get a mess.