I also meant the "spend a lot of effort" part to act as a qualifier, since for me true friendships tend to develop spontaneously and easily, in contrast to a situation where I'm actively courting the other person and they're kind of pulling back. In my own life, I've learned it's better to just let those second kinds of friendships die in the bud.

However, I recognize on reflection that for more introverted people, developing any friendship probably takes significant effort--so advice along the general lines of "if you have to push it, it's probably not meant to be" is actually probably bad advice for a lot of people. Instead, I think the question should be "would you be satisfied with friendship alone, if nothing further ever developed? Would the friendship be a source of happiness to you, or a source of frustration and pain?"

I just don't think guys should spend the time and energy being friends with women if friendship isn't truly what they're after. In a case like that it's much better for them to focus their attention on other women, who might reciprocate.

Fair enough. I can agree with that.