Monorail...monorail...monorail

Liking the idea of KL monorail. I'm still new enough to the game where I have plenty of room in Springfield but I have born witness to some anonymous friends who have been playing a while & have no room for much of anything. A bit off topic but I'm trying to stick to my "freemium" code & am slowly (emphasis on slowly) accruing donuts. I'm at max friend level & get donuts on a very random basis when visiting other Springfields. I was wondering if there was any pattern to such gifts or if it depended on the other Springfielder being in his/her town at the time. Any ideas or observations?