I noticed this a while back, while watching FFundercats, as they discussed the possible loss of the service, with founder Paul Buchheit. They also discussed why Friendfeed captured the audience it did and why most of the users hate/dislike Facebook. It’s the content and community that exists on each, and what value you receive from them. I ended up breaking the real-life social experience into 3 fields, to try and explain this.

Introduction

Commonality
A shared interest in similar items, friends, or favorite places to hang out or eat. It should be easily distinguishable to find a similarity to begin with as your mutual friend introduces you or you end up at the same location at the same time. You may both go to a place to enjoy a hobby you both share, and make a connection from that.

Mutual Experience
You have both being through an incident or event in which you share similar experiences, this could fall under commonality, but it is something that isn’t common enough that you would normally share with a stranger. It could be your profession, a disease that has affected your life, or going to an exclusive event. It is a personal connection that randomly comes out and creates an initial connection.

Notable Interaction
This is the kind that is often used in movies, but occurs quite often in life also, the cliche in films is when someone drops there books and gets assistance from someone. It’s just an accident that creates an opening for introductions. In real life this could be any unplanned event where people share some information about each other, whether it be a car accident, being stuck in an airport due to a delay, or any accident that causes people to offer assistance.

Acquaintance

Re-occurrence
The event that any of the aspects of the Introductory Field reoccurs often enough that you begin to know each other on a more personal level, than you would on a one-off meeting.

Mutual Shared Personal Knowledge
The information that most people don’t want you to have if they don’t know you very well, their birthday, their relationship status, where they’re from. It’s the most basic of info that provides accessibility to each other and also a little detail about one’s current state of affairs.

Caring
The use of Personal Knowledge to express yourself to the person. You can wish them a happy birthday, with out it being to awkward, or provide condolences when they lose something/someone very dear to them. It is the ability to express without being perceived as fake that you are willing to be there for the person in the moments they need support.

Friendship

Deep Interaction
The point in which you can discuss things that matter to you, that you might not share with people you don’t know very well. Discussions which involve personal knowledge to be gathered that isn’t public information. It is the ability to trust the other person with more personal information.

Experience
The effect of Deep Interaction is that you are begin to know more about the person. You have inside jokes, can pass on interests, and know how to change their mood for the positive or negative. The insight that comes with being a friend allows you to interact more fluidly with the other person.

Ease of Access
The ability to start a conversation with a person relatively simply, you make time for each other to have a discussion. It can also be, likely is, the provision of multiple channels to reach the person for such discussions. Having such ubiquity helps further and accelerate, the relationship.

Catalysts

Real-Time Discussion
By now we should all understand what this means, but I will clear the meaning up for those that don’t know. Real-time discussions are fluid interactions that happen rapidly enough, within a short period of time, that they can be seen as a seamless conversation.

Randomness
The spark that can ignite a friendship. It is the driving force of introductions and fosters connections. You see someone grasping something that you like as well, you have an accident, you trip. It is the key to mutual experiences, and notable interactions. It also keeps everything interesting, you may come across something new, at any time.

Currently, I haven’t found an online service that offers all of these qualities, but the top few have hit some sweet spots that make it much easier to manage socialization on all levels. Below I posted a chart of what factors Friendfeed, Facebook, and Twitter have become useful for. And I’m not saying that they don’t have ways to do all of this, it’s just not simple, if it’s not simple to manage the social factors, it’s useless.