I'm trying to utilise the who's online block at http://www.phpcodester.com/2011/04/drupal-7-block-for-whos-online-with-g...

After applying the patches suggested by various contributors this works fine in that it shows the contents of the sessions table.

However not all guests are listed in this table. However some are. So I have 2 questions:

Why are some guests shown in the session table and some not, i.e. what determines this?

Is there a way to make all guests appear in this table?

I'm considering just setting up my own table and capturing guest info in a PHP block, but I'd rather do this natively if possible.