I was thinking of removing/hiding admin-bar from my wordpress (3.1.1) installation.
I visited following link:
http://codex.wordpress.org/Plugin_API/Filter_Reference/show_admin_bar
I was surprised to see only a single line to remove/hide admin-bar
add_filter( 'show_admin_bar', '__return_false' );
My question is what is __return_false means? why __ and _?