They all inform you that they are thinking of leaving on a regular basis. So you should have many opportunities to encourage them if necessary. But you can't snap your fingers and force them out automatically.
I think so, as I was watching a video of WiiFolderJosh playing it and I saw an option when you talk to Isabelle called "Problematic Citizens" though im not 100% sure of what it does but it is possible thats is what it is used for... just dont take my word for it.
Waiting for: Animal Crossing New Leaf (3DS), Terraria (Vita) 3DS FC: 3652-1930-9604 (PM me your fc if you add me)
I think I saw that "problematic villagers" thing on a different blog. I believe one of the villagers had the phrase "girlfriend" and used it on a male player, so he reported it and Isabelle said that she would wash the villager's mouth out with soap. XD
Edit: TC, did you just insult the awesomeness that is Bob? Are you trying to start something?! (Just kidding, of course.)