Josh Olsen has a long story in the LA Weekly (October 10 2007) about his friend "Audrey" who fell in love with....a phantom. Literally. Audrey's true love, the deeply manly "Jesse", was entirely fabricated by a woman named Janna St. James.
I love this line by Olsen:
“You shouldn’t judge,” says Tania.
I beg to differ. This is why we have judgment.
Audrey is rescued from delusion by her friends, including Harlan Ellison (Boing Boing showed the way). But I think Josh is correct -- Janna will find another...victim.
"Audrey"'s blog on the whole sad mess
Karoli's post about the whole sad mess
Some other notable phantoms (people who didn't exist at all)
Not quite in the same genre, as Hart did it knowingly: Ray Caster
Princess Caraboo (1817)
Treva Thorneberry (I'd never heard of her, but her story has the common theme of the tortured past.)
JT Leroy (never existed, the fictional creation of Laura Albert, Geoffrey Knoop and Savanah Knoop).
There is, however, another equally important side to these impostors and hoaxes. Their stories should serve to illustrate the dangers of taking the abilities or phenomena associated with mysterious people uncritically at face value. Though most of the characters here are known to have lied, at the very least about their identities, they were believed by the majority to be exactly who or what they claimed to be, on the whole because people wanted to believe in what they did, who they were, or what they had to say. They were in a sense providing people with what they needed at a particular time, in a particular place. This is in fact the real danger in dealing with the unexplained and the mysterious, so many have the desire to believe in the unbelievable that objective judgment and criticism is crippled from the outset.
Identity and Heinous Behavior (l'affaires Sierra and Seipp)