I thought the B.City/W.Forest thing was mentioned before.
Someone explained it along the lines of (paraphrasing here)
Each person in B.City has an internal timer, and each day that you don't talk to them it gradually reduces until it reaches 0, where they will then pack up and leave.
(Sounds like Animal Crossing..)
also, @Serebii; Not sure if it's mentioned on the main site but about DW and DreamPoints:
3rd Berry Row: 1800 points
4th berry Row: 4200 points
Open Sky Area: 5000 points
Someone explained it along the lines of (paraphrasing here)
Each person in B.City has an internal timer, and each day that you don't talk to them it gradually reduces until it reaches 0, where they will then pack up and leave.
(Sounds like Animal Crossing..)
also, @Serebii; Not sure if it's mentioned on the main site but about DW and DreamPoints:
3rd Berry Row: 1800 points
4th berry Row: 4200 points
Open Sky Area: 5000 points