They are actually going to publish an article in Psychological Science saying that there is "doubt" as to whether true bisexuality exists in males.
http://www.nytimes.com/2005/07/05/health/05sex.html?incamp=article_popular 33 men that identify as bisexual does not a study make.
And I could go on and on as to why they got the results they did.
Edit: Replaced non working article with Times article
and here is a rebuttal artical
http://www.advocate.com/news_detail.asp?id=18543