I heard a discussion on BBC Radio 2 the other night between Simon Mayo and his guest Robin Dunbar, a British anthropologist who proposed that the maximum number of people with which a single person can have a stable, meaningful inter-personal relationship is 150. That is roughly the population size of a neolithic village, at about the time that humans developed language, and occurs because of the limits in the human brain to recognise and relate to other people in the tribe.

Now, that sounds immediately a tad nerdy but is interesting in a business world waking up to the explosion of web-based network marketing. Basically it means that you don't need to worry about having thousands of Twitter followers or Facebook friends and fans, you only need to build a smaller network of deeper, closer relationships.

After 150 or so (according to Dunbar) the network stops working efficiently and becomes a waste of time and resources. If you don't actually know the person or feel that you can do business with each other, there's maybe no need to add them to your network? Less really can be more!

A contentious view maybe but I think that, if anything, it helps to add realistic, achievable boundaries to the potentially unlimited reach of digital realtionship marketing. Concentrating on developing a network of 150 stakeholders can really be a useful, SMART objective for any organisation and one that gives a measurable purpose for the use of Twitter, Facebook, LinkedIn et al in the marketing communications mix.

For further info on Dunbar's Number go to http://en.wikipedia.org/wiki/Dunbar%27s_number