My son recently attended a wedding as his platonic friend's plus one. She was part of the wedding party. But...neither she nor my son had ever met the bride and groom in person. She and the other WP members were all part of an online group (I cannot recall the interest.) The wedding was Viking/Sky Rim themed, and my son was her plus one because he is into this type of thing. They flew cross country for this, had to rent a car, get a hotel, etc. He seemed to think it was no big deal, because this mama was thinking, 'Are they being lured to some elaborate sacrifice ritual?" I've met online friends in person before, but this seemed different, due to the distance and expense, as well as to the occasion.
In any case, they had a great time at the wedding and returned home in one piece, slightly poorer, but he doesn't regret going.
So is this a common thing? Have you invited online only friends to your wedding or attended theirs?