On Friendships

Of all the "ships" in the world, this is one that is the most under-rated...
Of course I know that most mature adults understand that friendship networks are really really important to their sense of well being, still it seems to me that we make do with whats available easily than actively searching for the friends who make us happy. Unlike relationships where everyone kind of knows that they are looking for "The One", its not the case with friends. Extroverts think anyone can be potentially a friend, introverts think no one can. But what if friendships are like relationships, maybe not requiring the same kind of exclusivity, but requiring time, commitment and effort both in searching for the right friends and then making sure they stay. Personally I find that some friends consistently make me better when I have contact while with others I am left wondering what was missing, why was it so ambiguous etc.
There are the unrequited friendships when one person wants to befriend another but its only one way, there are the expedient friendships, the fly by nights, the ones with benefits and so on...its quite a sociological mine! Economists have researched friendship networks to see (e.g. see Currarini, Jackson and Pin, 2009), they have impacts on health, e.g. drug use among teenagers, and other socio economic outcomes. But I wonder whether my friendships are driven by economics...I prefer not to think so...