Go on many bdsm-related social networking sites and chatrooms, and you'll find guys there who call themselves 'Master' So-and-so. I've never been convinced that a dominant should give themselves that title: I've always seen it as something others give.
I don't think I'm alone in this.
I know a sub who's often online in chatrooms and chatted up by men whose online names are 'Master' something or other. Her usual line is to ask politely on what basis they call themselves 'Master'.
This can lead to quite long exchanges in which she establishes they have no MA or MSc qualification; are not a master in a vocational sense (e.g. master baker, which is a recognised title), and are not recognised within their bdsm community as being a 'bondage master' or whatever.
She then points out that the other use of the term 'master' is an honorific title for young boys who have not yet reached the age at which they can be called 'mister' - and asks whether, in that case, they'd still like her to call them 'master'...
Personally I've always preferred to hear 'Ouch!' and 'You bastard!' rather than 'Please Master!' but maybe that's just me.
(Sorry about the lack of posts, I've been away for a few days but normal service is now resumed.)