How do you define who is your friend?

I had a rather interesting discussion, with an American colleague about how different cultures define friendship.



I find that Americans are rather quick to use the label. Which at first, seems like a good thing. But as a result, American friendships clearly lack the depth or meaningfulness that they do in many other cultures. Most American friendships would barely qualify as acquaintanceships in European countries.



I imagine this is how rhetorical phrases like "how are you?" and "how's it going?" turned into the American equivalent of "hello".



Facebook I feel has taken this trend to its logical conclusion, and labels anyone you know, who you don't openly dislike a "friend".



I'm curious though, how do people here define friends? Can someone be your friend if you've never been to their house? Would you ask them for help if you were in trouble? Etc.