Last night I went to the wedding of someone I know from, um, college. The word had gotten out that people who knew the couple, but were not formally invited, were welcome to come anyway. And indeed, when we got there, on the name-card table there was a sign which said something like "Anyone who doesn't have a card - feel welcome to come in and sit at one of the open tables!" These open tables turned out to be something like a third of the wedding hall, and they were mostly full.
I don't know if this was typical for Israeli weddings (this is the first one I've been to), but it left me with a very good feeling. The chupah is shaped like a tent without walls. As such is bears a striking resemblance to Avraham and Sarah's tent according to the midrash, which was also open on all four sides, so as to encourage guests to visit and partake in their hospitality. By implicitly welcoming and invitating anyone who might come along, the couple gave us a nice reminder of the behavior of Avraham and Sarah. I can't imagine a more auspicious beginning to one's married life.