What is Friendship?

In ancient times, friendship was a major topic of philosophical speculation. Aristotle to Marcus Aurelius had deep concern about friendship and how this relationship effected one's life and ethical actions.  Today, friendship seems less of a focus, and more of an assumption.  Romance and sex take center stage, but friendship seems not so significant.

This seems even more so with the advent of Facebook and it's use of relational terms which seems to minimize one's relationship to the most shallow degree.  We are "friends" with people whom we barely know or don't know at all.  We "like" opinions and jokes that we might only have barely understood, let alone approved of.  We comment on each other's status' only barely brushing each others' souls. Is this what friendship constitutes?

Yet is the physical connection to our friends too emphasized?  Just because our friend is across the country from us, does that make us less of friends?  It might be that we have lost touch, but that is less true in our world of internet connection.  Often the internet allows us to connect to people more deeply than when we saw each other face to face.  But are we missing something?  We certainly do not hear the sarcasm in one's voice or the wink of the eye.  Internet connection is little more than glorified pen pals. Does physical presence truly add more to a friendship?  Also, if everyone we know is a "friend" does that minimize what friendship really is?

What is the essence of friendship?  We can have friendships based around one subject, even just a hobby.  We can have a friendship that develops through small talk about one's family.  We can have a friendship in which we discuss the deepest aspects of our emotions, but we never see each other's partners.  What is friendship based on?  A mutual subject of agreement?  Enjoyment of the other's company?  Common activities, whether it be horse racing or drinking coffee?

What is the "social contract" of friendship?  Each relationship has unspoken agreements.  For a marriage it is often sexual faithfulness and mutual financial support.  In the workplace an employer agrees to pay employee for the employee's service and obedience.  What about friendship?  Is there an agreement to agree?  An agreement to be open about certain topics?  A hidden agreement to support each other on certain subjects, even in opposition to each others' families?  An agreement to help each other out in dire times of need?  This "contract" is certainly different with different relationships, but how is such a contract determined, since we almost never discuss aloud how our relationship works, yet we have an agreement as to how it does?

What is the relationship to friendship and marriage or co-habitation?  Is a boy- or girl-friend just a "friend with benefits" or is there more to it than that?  Is an acquaintance just a friend-in-training, or is it a completely different relationship?