Look, I don't know if I'm going to manage to keep up with the speed this thread is moving at but...
First of all, nothing between consenting adults is actually wrong. But if you don't want to do it, there's no reason why you should. Secondly, stuff that doesn't hurt or scare you but seems a bit daft, why not try it once in a while in return for your partner doing something that he/she thinks is a bit silly but which works for you (whether that's really corny romantic dinner and music or pretending to be a randy waterbuffalo...) If anyone's partners are nagging on and on about something and not respecting the other partner's viewpoing then it doesn't matter if the request is for sex with the light on or a full rubber-nursey-enema treatment: bullying isn't the way to get what you want.
As to threesomes, you know, people do have them and enjoy them and suffer no consequences. The best way to do so is to have a proper, sensible discussion about it first and agree on a no-blame policy if it doesn't work out. Generally, if you want a threesome without becoming the talk of the local primary school/your workplace, using either a contact site or your local swingers' club tends to mean that whoever you hook up with will have some idea of what they are doing.
Also, actually, if you and your partner both sort of fancy the idea of playing with other people together, go to a swingers' club just to look, and check it out: sometimes couples (even those who swing regularly in clubs) never actually have sex with other peoole, they just like having sex near other peole who are doing the same.
Oh, and while I'm here, I'd just like to [blow enormous rasperry] at the people who thought my thread on sexual attitudes was too rude. You must all have burst into flames by now.