I think if someone is going to a play party or is in the early stages of a power exchange relationship with someone, dis-allowing a safeword isn't fair.

At the same time however, I don't believe a safeword actually keeps you safe. If the other person is bigger than you and stronger than you or has you restrained, then they have the power, not you. No matter how much you would like to convince yourself otherwise.

If such an individual is not a trustworthy person, then your safeword will not keep you safe.

In a more full TPE type relationship I think of a safeword more as an "information exchange" where the submissive/slave is expressing honestly his/her limits of tolerance being reached. Then the Master can determine from that point what to do, but if one has truly given over full power and control and is truly owned, then they cannot give edicts.

At the same time though, a loving Master/Mistress would most likely listen to a safeword even if it was only given for informational purposes in the interest of not bringing physical or psychological harm to his slave/submissive. To ignore something like that is to break trust, possibly irreparably.