As with any type of collecting, it is a HUGE deal to those that collect the Disney pins! At DTD I saw special tables set up and people opening their binder of pins to trade with others. At the Disneyana Conventions you can purchase special sets of pins, and they have a meeting room filled with vendors selling all sorts of pins from all of the parks worldwide, etc. I started collecting back in 2000, but am not very serious about it as some are. I just bought ones that appealed to me. This last trip was our son's first, so I picked up pins that he would like (the year pin, first trip, train, monorail, his favorite rides, shows, characters, etc). Ive also found some on Ebay. I had a few that light up, which he gets a kick out of. I also picked up a guest of honor badge for him as well. Now they hang on a Mickey lanyard in his room along with his Mickey hat to remind him of his trip. They have pins for everything Disney. Its unreal! Every even has a pin. There are limited edition pins, some that light up, some play music, etc. There are kiosks all over in each park. You can trade with cast members (they have some hard to get ones) and anyone else (a great way to meet people too). DTD has a huge pin shop as well. They arent cheap and add up very quickly, so control yourself! They do have little starter sets which are fun.
alison