Path dependence is a term used to explain how the "set of decisions one faces for any given circumstance is limited by the decisions one has made in the past, even though past circumstances may no longer be relevant Path dependence is a digital form of a Skeuomorph.
Once a person or society is used used to doing things one way, it's really hard to start over and start doing things another way. People significantly down one path are difficult to move onto another path and to change direction. Path dependence in terms of people, would be someone who uses a landline phone and writes letters as a primary form of communication. Their path dependence makes it difficult for them to use new forms of technology. In this case, it takes an external change with large enough magnitude to get those on path dependence onto another path. The best example of this is Facebook.
What ends up happening is that they lose touch with their kids because their kids have switched to a different communication medium and are no longer readily available on phone or by letter. In order to not be left out of social culture, they have to adapt, and Facebook takes what they had before with letter writing and phone calls and makes it easy to access and digest. Sometimes the adoption skips a generation as it is grandparents that are often more alienated than parents because of modern society's tendency to separate grandparents in different house from their grandchildren and children.
- Definition from Praeger, Dave. Our Love Of Sewers: A Lesson in Path Dependence http://poopthebook.com/blog/2007/06/15/sewers-path-dependence/. Published 15 June 2008. Accessed Oct 2011. Quoted in the Wikipedia article Path Dependence. http://en.wikipedia.org/wiki/Path_dependence#cite_note-0