Can A Straight Guy Fall In Love With A Gay Guy?

This probably and age old question, but can a straight guy really fall in love with a gay guy?  I've heard answers like 'anything is possible under the sun', it may be true but not a satisfactory answer to the question.  Some said that if a straight guy fall in love with a guy gay, then he is not really a straight guy.  He may not be totally gay but at least he's bisexual.

Any other views out there? or better yet, personal experiences?