We all have a problem keeping up with friends and family that have moved away. The problem is simple: we, as humans, can only have so many relationships as priorities in our lives, and we naturally move the people we can see and interact with to the top of our lists.

To put it more strongly, people who have moved away become concepts, or abstracted representations of real people. When we think about them we remember what they used to be like, and we consider re-pinging them to see if they’re still “alive”. This represents an invisible obstacle, one that sadly keeps many from contacting each other for years or decades. It literally becomes a “big deal” to track down and reach out to someone who’s lost their tangible status in your mind.

Twitter works because it proves to our subconscious, even if only temporarily, that your extremely close friend that moved away four years ago is in fact still real and tangible. It removes the contact barrier and makes them approachable.

Of course, this is what all social applications strive for. The difference is that most social apps struggle with two things: they require users to be at a computer or to use a mobile email client. They have barriers to contact, in other words.

Twitter, on the other hand, by having the deepest personal penetration (mobile phone) combined with the most ease of use (text message), has an effort rating that falls below most people’s natural resistance to participate, and its positive reward ratio is much higher because people are far more likely to respond to a text message than almost anything else.

That’s why Twitter works: it has a low enough friction to overcome the resistance to use it, and has far more chance of achieving interactive success because it penetrates all the way to the recipient’s mobile phone via text message. Once these two things are achieved you’ve done what all social technology is meant to do: it strengthens the connections between people.