I’ve never been in the camp of those who follow back every one who adds them on social networks. While the reason people reciprocate all follows–it does seem the polite thing to do–is understandable, I know I’ll never be able to have any kind of meaningful interaction with all of them (over 6,000 now on Twitter). So to me, it seems the more courteous thing to do is not to follow everyone back, but to make sure I respond to anyone who sends an @ message to me.

My question in this blog post is to ask how you determine your “friending” policy on social networks, especially Twitter.

Yesterday I started a TwtPoll to ask the question. Of course, this is not a scientific survey, and is only a small sample of people–83 people who follow me on Twitter or who follow someone who kindly retweeted the poll for me. And the number 1,000 is an arbitrary threshold.

The results, frankly, surprised me a bit. I thought there might be more who valued reciprocity so highly they would unfollow someone who doesn’t follow them back. That is certainly the gambit of those trying to amass followers as quickly as possible, since Twitter seems to limit a person to following 2,000 people or 110 percent of those who follow them, whichever is higher.

But the vast majority of respondents indicated that it either didn’t matter whether I follow them back (46%) or that it was fine as long as I made an effort to respond to messages directed to me (42%). As Dave Shaw said, “Following is the ultimate opt-in and doesn’t require a follow back. Nice but not required. Responding to @’s and DM’s is just good manners.” (Please click through to the poll to read all the comments.)

As a result of the poll, I will be trimming back the number of people I follow on Twitter. If I can’t remember having any exchanges with someone, I’ll drop that person. Why? Because I’m following over 1,200 people but only paying attention to a few hundred at most.

And that meshes with the well-known Dunbar number, an estimation of the number of people with which one can realistically maintain relationships. For “real-life” friends, the average number is 150, with some people able to keep track of around 300.

I share Ross Mayfield’s view that social software allows us to augment the Dunbar number, which he based on the size of the neocortex in primates and then extrapolated to humans. Ross cites recent research that shows:

Twitter users have a very small number of friends compared to the number of followers and followees they declare. This implies the existence of two different networks: a very dense one made up of followers and followees, and a sparser and simpler network of actual friends. The latter proves to be a more influential network in driving Twitter usage.

That describes my experience. When I was using Twitter exclusively on the Web, I was easily following 500 people. Using tools like Twhirl and TweetDeck, I began to follow more people. TweetDeck gives the illusion of following 1,200+ people. But in reality, I ignore most of them. As the research shows, I have a group of “top friends” I keep in contact with by using the Group feature in TweetDeck. And the rest I try to read now and then–but that turns out to be so infrequently that those other people might as well not be on my “following” list.

This topic has been on my mind since attending a salon discussion at South by Southwest Interactive led by David Armano and Russ Unger. Summarizing his thoughts about the Friendship Is Dead conversation and the concept of ambient intimacy on his Logic + Emotion blog, David concluded:

Most of us intuitively know who our friends are. … But, with networks we have access to more individuals then ever before in history. We know when they are sick, when they are traveling and even when they’ve lost a loved one. Some of us stay in constant communication with people who would have normally been considered “loose ties”, people we’ve met at an event, a party, a former co-worker, or college friend. These ties can become strengthened and feel like something more than they used to be.

What are your thoughts on the relevance of the Dunbar number to social networks and the proper etiquette for following people on Twitter?