Otherwise good product and easy to set up and use. Easy to set up article to view presentation with simple tags.
You’re completely right! This is a 'lack of functionality' of slideboom.
However, if you generate a local flash file with their 'Free Powerpoint to Flash Converter', upload it to your website's server and publish it with one of many Joomla! flash viewers, you’ll have a 'private' presentation.
Not as nice when using my plugin... Thinking of that... I might include such an option in a future version!