No - if all parties are heterosexual.

Yes - if the initiating partner is bi sexual and the third party is homosexual corresponding to the first party's sex.

I've done this and it was great; the bisexual girlfriend had everything she wanted at once and there were no issues between me and the lesbian partner.

But I just don't want to suck a guy off thanks anyway and his cock up my arse and in my partner in the same session - uhh no!

Interisting situation - as an open minded guy I think I would agree to it, but I would have to see the guy first chat to him a little, so it is very circumstantial.

Have been there and done that.

Won't ever happen ... but if my wife asked me to ... I probably would for her. Not something I would likely initiate, however.