I just want to invite everyone we've ever met in our whole entire lives.
It'd be a lot easier than trying to keep it below a certain number. You think you're good inviting close friends and family. But then, it starts happening.
So and so is coming from out of town, therefore they won't have anyone to watch their kids = kids have to be invited, too.
This person is invited, so this other person needs to be invited, too (can't have anyone getting offended).
This couple needs to be sent an invitation, but just out of courtesy. They probably won't actually COME. (But what if they do??)
The guest list is one part of wedding planning that I'll definitely be grateful to have DONE.