There are a number of misuses of gnome_vfs_uri_is_local() in the
libgnome-desktop/gnome-desktop-item.c file.  These cause, for example,
gnome-panel launchers that use "%f" to fail to send the %f argument to the
launched application when the file is on an NFS mounted volume.

Normally, %f should send the file name (ie NOT a URL) to the launched
application.  %F _does_ indeed work, but %f fails when the directory that
the argument comes from (like ~/Desktop for homedirs) is network-mounted. 
The get_first_*() functions are guilty of this bug.

static char *
get_first_file (GSList **arg_ptr)
{
	while (*arg_ptr != NULL) {
		GnomeVFSURI *uri = (*arg_ptr)->data;
		if (gnome_vfs_uri_is_local (uri)) {
			char *path;
			path = g_strdup (gnome_vfs_uri_get_path (uri));
			return path;
		}
		*arg_ptr = (*arg_ptr)->next;
	}

	return NULL;
}

Here, since this function is called from the %f substitution block lower
down, the gnome_vfs_uri_is_local() skips over any object that is on a
network mount, as all objects in my homedir are.