what is the purpose of social networking sites

Today in our tutorial session, we discussed what social networking sites provide, and we didn't come to any conclusion.
It does appear in some cases that they may help keep people in contact with others. However, we generally agreed that it only helps stay in contact with people who are marginal friendships anyway - that we maintain traditional contact with our more meaningful relationships.

One suggestion was that despite being very public, the sites actually allow us to be more private, not having to maintain the less meaningful relationships, instead allowing us to update these contacts via our virtual monologues.

So what do these sites advertise themselves for?
Facebook:
Facebook is a social utility that connects people with friends and others who work, study and live around them. People use Facebook to keep up with friends, upload an unlimited number of photos, share links and videos, and learn more about the people they meet.
Discover the people around you
Facebook is made up of many networks, each based around a company, region, or school. Join the networks that reflect your real-life communities to learn more about the people who work, live, or study around you.

MySpace
:
MySpace is an online community that lets you meet your friends' friends.

Create a community on MySpace and you can share photos, journals and interests with your growing network of mutual friends!

See who knows who, or how you are connected. Find out if you really are six people away from Kevin Bacon.

MySpace is for everyone:
• Friends who want to talk Online
• Single people who want to meet other Singles
• Matchmakers who want to connect their friends with other friends
• Families who want to keep in touch--map your Family Tree
• Business people and co-workers interested in networking
• Classmates and study partners
• Anyone looking for long lost friends!


Friendster:
With more than 75 million members worldwide, Friendster is a leading global online social network. Friendster is focused on helping people stay in touch with friends and discover new people and things that are important to them.

Unfortunately Bebo was down so I wasn't able to get their stated purpose.

So what is the advertised purpose?
1. Reconnect lost friendships
2. Stay in touch with family and friends
3. Find potential new contacts.
4. Visualise the invisible lines of connection that we normally do not see.

Of these reasons, 1 & 2 do not seem unique to the internet - that is that the same function could be done via email, telephone, or even traditional mail.

Based on our discussions, the third reason seemed fairly dubious, in that few new relationships seem to be forged through these websites, although our experience is not necessarily the same for everyone. It would be interesting to find some statistics regarding how effective these websites are in this category.

The fourth reason is actually the most interesting reason, which mandates the use of web 2.0 technologies. Occasionally we may find ourselves on a plane next to another passenger and if we decide to actually engage in conversation we may discover some connection with them. It is only through significant work that we start to reveal these relationship patterns. Sites such as facebook allow us to see the larger networks in which we are connect in a quick and easy way (for example, I keep getting a friend recommendation for a political figure in Washington, DC that was significant in unveiling the lies in the lead up to the Iraq war. I have never met this person, have only seen him on TV, but a friend of a friend worked with him and is friends with him.)

This visualisation of these unseen relationship networks is the one unique feature of social networking sites, which cannot be easily replicated in the physical world.

Is there a problem in the fact this very unique feature is not more notably featured?