I've been in several parties where all three of us go to kick a player (via right-clicking on the player's tile in the upper left corner) and nothing happens. We were only able to kick an idling player once when I stood next to him, selected "Kick", and received a modal window to insert a reason. The rest of the party received the vote and he was kicked.
What are the conditions for actually booting a player? Do you have to stand near him? Does there need to be a period of time in-between the first vote and the actual vote? Is it a majority vote or a consensus vote, and how does it differ between four-, three-, and two-person parties?