A post on Read Write Web explains how Old Spice created its very successful Youtube (not forgetting all the other other networks) content.

The man in charge of the project, Ian Tait, at Old Spice's marketing agency Wieden + Kennedy put the success down to good collaboration between tech pros, social media pros and the creative team.

The idea is simple but the use of social media networks was very well thought out and executed. It is good fun too, which helps.