I finally got Web2py running under Mountain Lion Server with mod_wsgi. It took me so much time that I would like to share in case somebody else might be stuck as I did.
The solution has two steps:
1. Editing the new Apache config file Mountain Lion Server uses instead of the which comes with Apache.
2. Change the mod_wsgi configuration file presented in page 519 of your book.
The first one consists in changing the AddHandler command in line 383 of file:
from: AddHandler cgi-script .cgi .pl .rb .py
to: AddHandler cgi-script .cgi .pl .rb
The second consists in removing the two lines starting with:
because Apache in Mountain Lion is compiled as Preforked and cannot wsgi cannot run in Daemon mode.