From a security standpoint this is a very bad, bad idea. The whole purpose of the 'nobody' account is that it has NO special privileges. Nothing should be owned by it, nothing should be available just to it. If you want something readable or executable to 'nobody', you should do so by making your file/script world-readable and -executable. If you have a problem with that, you should set up your users/groups/ownerships a bit differently (running the web server/whatever as a real user, for example). Any potentially insecure daemon that runs as nobody and is broken into would, in theory, be restricted to the 'nobody' user, which means they shouldn't be able to do anything to any files (though they might be able to fill up, say, /tmp). If you give them ownership of a bunch of files like your web docs/CGI scripts, even with a restrictive set of permissions, they're just one chmod shy of defacing your site and finding ways of elevating their privileges further.

Granted, with a suitably equipped intruder, even with the 'nobody' account they can find ways of getting deeper into your system with any local account, most intruders of this nature can not, and only through script-kiddie-friendly installations such as this do they get to deface web sites without working outside of the user the web server runs as.