Kikker

He refuses to open the door for free, he doesn't refuse to unlock the door as a whole. Person A isn't trapped indefinitely, he can get out, it only takes him a day of work. Maybe a scenario with a broken lock in a public restroom makes more sense. In that case a malfunction causes Person A to be trapped instead of another person. Is person A really imprisoned though? He is able to get out within a day. Furthermore he was accidentally trapped, which is very unlikely I admit, by the host. The host doesn't prevent Person A from escaping his current situation. He does however refuse to service Person A for free. But you'll probably argue that the host is responsible for his actions even if it wasn't his intent. In that case it doesn't matter whether he was imprisoned or not since the host is still responsible for any disadvantage person A receives. More interesting is a scenario in which person A traps himself or is trapped by a third party. Would that be a voluntary exchange if all other factors remain the same? Or would the location need to change on neutral ground, let's say a public restroom with a broken lock, for it to be a voluntary exchange? Or is something else making it involuntary?

Well if you do some basic math, in the period of 2008-2010 42466 people were lifted from India and china per day based on that source. (445-400+173-156)/(2010-2008)/365/2 = 42466 People per day

So what prevents an militarized insurance company from aggressively blackmailing people to pay contributions? You would need to militarize yourself or you would insure a second time against that insurance company. Logically there is also nothing to prevent the second company to aggressively blackmail people for contributions. You would need to militarize yourself against that second insurance or take a third insurance to insure against the insurance against insurance. It's a never ending cycle.

I would like to propose a situation in which I'm not sure if a robbery or a voluntary exchange has taken place. Keywords are voluntarism, intention and consequence. Full context Let's say Person A is invited to a small house party. He shows up, greets the guests and starts wandering around. Eventually person A wanders into the basement where he enjoys the view of some antique objects. Meanwhile the host of the party sees the open basement door and locks it to stop guests wandering in there. During this he remained unaware of person a who is still in the basement. The Guests already started leaving so persons at the party assume Person A has left. Person A eventually becomes aware of his situation as he tries to leave, he is however unable to contact anyone during the party. When the party is over and the host is cleaning up he wanders near the basement door and hears Person A trying to make contact. He decides to make use of the situation and proposes a deal where person A would pay him 500$ to perform the service of unlocking the door. Person A accepts this deal as he rationalizes that it would take him a day to break out of the basement and that day would be worth about 500$ to him. Summarized. Person A chooses to go to an event where he is unintentionally put in a disadvantaged position in which the host can demand high pay for minimal effort. Did Person A and the host perform a voluntary exchange? Or did Person A get robbed?