I've had two instances where co-workers specifically told me that I was going to be invited to their weddings. They even asked for my advice regarding some of the wedding preparations and on a few issues that they were having with some of their bridesmaids or family. In the end, I was never sent a wedding invitation by either person and I just assumed that they probably had to cut back on the number of people attending the reception to save on costs. No apologies or explanation were ever offered and I honestly didn't expect one. However, one of my other co-workers was quite miffed about the whole thing (she was also invited verbally but never received a formal/mailed invitation to the wedding).