I think that Save the Date cards are such a good idea. I had never seen then until my cousin sent me one when she was planning her wedding. As bridal invitations have to be sent so close to the event and most weddings happen in the summer, it is such a good idea to give guests some prior warning that they need to keep that particular date free, if they want to attend. People are planning weddings earlier and earlier these days in order to ensure they get the venue that they want. This means that they can know for over a year in advance. If there are people that are very special to them, that they want to make sure can attend, then it is a good idea to send out the cards as they are unlikely to have planned anything else that far in advance and so will know not to do so. It is certainly becoming a popular idea which is great and I am sure it will be something that most people will do soon. I would definitely do that if I was getting married but I am already and do not plan to do so again!