You donate Gotchi Points to get souvenirs from the Gotchi King of Tamatown. Once you have all 3 souvenirs, you get a password for Tamagotchi Connexion: Corner Shop 2 on the Nintendo DS.
As for the robber, maybe you were just unlucky that time! One time I got robber twice in one day. What you get in the mail is tied to your Fortune Cookie. In fact a lot of things is tied to your Fortune Cookie, therefore you seem to get heaps of Fortune Cookies a day.