No, not necessarily. It depends on what he wants to do, as well. If he wants to do something other than teach, then a postdoc is just fine. It's, just as Jordy said, sometimes a "journeymen" step along the way. I can be exploitive but it's unlikely that your daughter's bf is going to suffer the same plight as English and history majors who are in disciplines just flooded with people competing for university positions. He's got opps in academic, the private sector, and the public sector. A postdoc, if it's at a place where he wants to network could be quite rewarding for him. As I said, my mentor's son did a stint at -- I've forgotten where -- and then landed a gig at Cornell. He then went on to U Mich Ann Arbor (associate), then he went off to Rutger's (2004) als as an associate prof.
Cool! Now I went and looked him up and his has a blog with his brother! :)
Bitch | Lab http://blog.pulpculture.org