Straight, Gay or Lying?

This article in the NY Times is interesting. Some excerpts:
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The study, by a team of psychologists in Chicago and Toronto, lends support to those who have long been skeptical that bisexuality is a distinct and stable sexual orientation.
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In the new study, a team of psychologists directly measured genital arousal patterns in response to images of men and women. The psychologists found that men who identified themselves as bisexual were in fact exclusively aroused by either one sex or the other, usually by other men.
...In the experiment, psychologists at Northwestern University and the Center for Addiction and Mental Health in Toronto used advertisements in gay and alternative newspapers to recruit 101 young adult men. Thirty-three of the men identified themselves as bisexual, 30 as straight and 38 as homosexual.
The researchers asked the men about their sexual desires and rated them on a scale from 0 to 6 on sexual orientation, with 0 to 1 indicating heterosexuality, and 5 to 6 indicating homosexuality. Bisexuality was measured by scores in the middle range.
Seated alone in a laboratory room, the men then watched a series of erotic movies, some involving only women, others involving only men.
Using a sensor to monitor sexual arousal, the researchers found what they expected: gay men showed arousal to images of men and little arousal to images of women, and heterosexual men showed arousal to women but not to men.
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"I'm not denying that bisexual behavior exists," said Dr. Bailey, "but I am saying that in men there's no hint that true bisexual arousal exists, and that for men arousal is orientation."

This comment within the article is particulary interesting:
John Campbell, 36, a Web designer in Orange County, Calif., who describes himself as bisexual, also said he was skeptical of the findings.
Mr. Campbell said he had been strongly attracted to both sexes since he was sexually aware, although all his long-term relationships had been with women. "In my case I have been accused of being heterosexual, but I also feel a need for sex with men," he said.

So, is it a continuum? Is it a function of with whom you want to/can have an emotional relationship with? Just some food for thought...