I don't think you have to be a lesbian. I certainly don't consider myself a lesbian or even *really* bisexual (I've never dated a woman) though I have considered serving a Mistress in the past.

Since I am not really a lesbian though, and would never want to give up men completely, the more likely thing that would ever happen is my Master ordering me to serve a Domme (though I'm not sure if He wants anyone else ordering me around :-P ).

Actually... come to think of it... forced homosexual behavior when you consider yourself heterosexual can be quite humiliating and kind of hot...

Anyway! I got off on a tangent fantasy there.... the point is, no. I think you can just like to serve :-)