Well, the people putting up bounties, are spending money. Those putting up items wants to get money, so I think the comparison is flawed. As for who cares, since they are players as well, I think what they wants is as valid as anyone else. But I see we disagree here.
As for the abusable point, I see that might be a problem. But since they will be protected again as soon as the bounty is gone, and if there is a bounty cooldown period, my opinion is that the abuse will be a minor problem.
Bounties is a part of the game. People harassed by duellers put bounties on them to get even. The usual response is that they can respec instead, but if this is the only answer, why bother with bounties at all? As it is, the only one earning the bounties are other duellers.
It could also be that the free for all would be activated when the bounty reach a certain sum, several people put a bounty on someone or something else. That is why I would like to discuss it. But if I am the only one, I'll let this be the last post.