From NY Mag:
Just How Preposterous Is the Fantasy of No-Strings Threesomes? By Maureen O'Connor
[…]
Three-way sex may have a reputation as libertinish, profligate, promiscuous. But in just about every way the three-way defies and distorts the no-strings plus-one fantasy — instead reflecting and refracting our understanding of commitment. Beginning with what it means to couples, who often see it as a way of branching out. But the more I talked to couples about their threesomes, the more it seemed a third person forces the other two to realize exactly how much — or little — they have in common. At a time when the most universal sexual imperatives seem to be communication and shared pleasure, three-ways have shifted toward the cult of romance — sexual fantasy sublimated into intense coupling. They’re for the couple who share everything, including mistresses. Assuming, of course, they can find a willing mistress. “They should call this app Unicorn Hunter,” a straight 31-year-old grumbled to me on 3nder.
[…]
But even among those more likely to visit New Zealand, three-ways remain a common form of monogamist escapist fantasy. My friend Maya (her name and some others have been changed) considers three-way flirtation the ultimate win-win “sexual white lie”: “Just hot enough to make you sound kinky, without being kinky enough to scare off more conservative men. And the logistics involved are so intricate that it’s rarely going to come to fruition anyway.” Normally, she considers herself “too insecure and afraid of getting left out to actually do it,” articulating a common three-way fear: jealousy and rivalry breaking the couple apart.