Just when the world is coming to grips with the idea that homosexuality is innate, along comes a Sex and the City actress to throw a spanner in it.

Born this way? Apparently not, for Cynthia Nixon at least.

According to an article published in the New York Times magazine, Nixon claims to be "gay by choice" following a 15-year relationship with the father of her two children which ended in 2003.  A year ago Nixon had a child with finance/partner Christine Marinoni.

“[F]or me, it is a choice. I understand that for many people it’s not, but for me, it’s a choice, and you don’t get to define my gayness for me,” said Nixon. “…Why can’t it be a choice? Why is that any less legitimate?”

Her stance is causing some consternation among the homosexual community who regard "her switch in sexual orientation as disingenuous." Basically: either you are or you aren't. Sexual orientation isn't a fashion; it isn't something you pick up on a whim, then ditch just as easily.

Or is it? Celebrity gossip blogger Perez Hilton admits it may have been a choice for Nixon but not for legions of others who were born gay.

“I don’t pull out the ‘bisexual’ word because nobody likes the bisexuals," Ms. Nixon explained to The Daily Best. Everybody likes to dump on the bisexuals.”

Is sexual orientation cut and dry? Are people are either gay or straight, or in some cases, like Nixon, a bit of both? Do such distinctions even matter today?