$user = &JFactory::getUser();

$uid = $user->get('id'); //works 
$umail = $user->get('email'); //works 
$unamed = $user->get('posname'); //does not work

Why can't I personally use JFactory to obtain the fields which i have added on my own around the Joomla user table. Can there be another simple way they may be become?

You'll need the usermeta wordpress plugin as posname isn't area of the user model

http://joomlacode.org/gf/project/usermeta/