> 'Let's work for free for a rich guy' is hardly 
  > what I call a good idea.

The whole thing might not be as economically irrational as it might seem at first. Seth Godin is a brand with a large value. Nukomeet is a consulting company and presumably the time they put into the project is returned in the form of a work that can be referenced when pitching work to new clients. For Nukomeet, it's an investment in marketing.