Well, what are the advantages of a 3-some? Hard to put into words but here goes.
- the erotic and sexually stimulating opportunity to either have sex with another person while your partner is present.
- the opportunity to see your partner having sex with someone else. (if that's your thing)
- the opportunity of having 2 members of the opposite sex tending to your needs and desires, as well as you to theirs. ( some guys/gals love the challenge)
- the bisexual factor is in there as well...perhaps an opportunity to experiment for the first time, or to fill the need.
- the chance to either try or fulfill the need for voyeurism or an exhibitionism.
The disadvantages:
- hurt feelings
- jealousy
- relationships between friends or partners forever changed or even ruined.
- insecurities develop, or increase, especially if one person feels insecure about their relationship already.
- infidelity...perhaps 2 of the 3 involved, will agree to meet at another time for a little 1 on 1.
- embarrassment....not being able to go through with it after the ball starts.
Bottom line, sounds like fun, just make sure all parties involved know the deal going in.
Make rules...and follow them.