i would have to agree with denu on this one. what is considered acceptable by some is not-so-much with others. the meaning and level of importance behind each and every bdsm title is different for everyone...whether it be per person, per relationship, per group, or so on...

that being said...i, myself, would never even consider calling someone Master unless they were to own me...for me, that title holds too much meaning. and if anyone had objections to this, they would need to be taking it up with my owner...who, i can imagine, would be explaining that he would never expect me do such a thing to start with.