If you are installing Joomla via cPanel's File Manager to your mywebsite.com (user mywebsite) account, you will upload the package to your server and extract the archive. All files will have the user and group according to your account mywebsite:mywebsite. You will have to change around three dozen directories and files and make them writable: http://goo.gl/EYjIPW and you can go ahead with the installation. All files created during the installation and later, using the Joomla platform will have the user and group nobody:nobody.
If you chown all extracted files to nobody:nobody, prior to installation, you won't have to bother about making the above-mentioned directories writable plus more than likely you will not run into any "Permission denied" errors later (changing the owner can be done after the installation as well).
The question, do you know any drawbacks of having the files owned by nobody:nobody? What are the pros and cons? And what about the files that are created by Joomla during and after the installation, these are by default owned by nobody:nobody.