A moment of seriousness; If a guy is a good frirend to another guy, it should at least factor into his thinking as to whether or not to actually go after a woman his friend has dated/has a major crush on.
However, I think women, based on reading in this thread, take that to a higher level; as in, if I know my friend is interested in him, I wouldn't go out with him..much more a definite deal than it is with the guy.
If a man is interested, or falls in love enough with a woman, he will NOT let friendship keep him from 'making his move'...that's my own way of thinking..I would agree that not all guys are that way.
But, if I were fully convinced that the woman I love was about to marry another man, the only thing that might stop me from going to her and making my case would be pride..it would not be friendship with another guy.
YMMV, of course. (Your Mileage May Vary)