One thing about the invites that I have found to be noteworthy is the finality of it. It is almost like you draw a line and on one side are "people invited to the wedding" and on the other side is "people NOT invited to the wedding." The people invited are the glorious friends and family members that made the list. Feel free to call, email, text or communicate with them in anyway. You can feel comfortable talking about any details about the wedding and when the wedding is over I am sure that you will no doubt show them the pictures.
The ones that are not invited to the wedding though is a different story. On this list could be former great (best?) friends, roommates or even new friends who you just recently met. This list seems so final. It is almost like you had always said to yourself "sure *Francisco and I don't really talk any more, but maybe someday will get back to being friends." Now with the wedding invites it is almost as if you have given up all hope of them being your friend again. You have come to the realization that that friendship has run its course and you just have to move on. In my mind it is the closest thing to a "breakup" that a friendship has since one breaks up with significant others, but doesn't really do the same with friends.
*I'm watching Liriano pitch against the Tigers right now and obviously didn't want to use a real name.
Anyway, I still hold out hope that under different circumstances that some friendships can be regained. If that day comes I hope that they are ok with the fact that they weren't invited to the wedding. My guess is that it isn't nearly as big of deal to them as it is to me.