Accounts connected without abusing the campaign probably won't be a problem, but if they join the same campaign then therein lies the problem.
I agree with your first point that if anyone create and/or operate multi accounts then that is not a problem until that abuse any campaign or use to scam. But on the second part it should not be problem too until they use multi account on same campaign if the bounty/campaign manager allow to join or do not forbid to join on by multi account.