Thanks for using our answers forum! I understand that you're wondering if there can be more than one user at a time? Well, yes you definitely can add a guest password which will allow someone to access your Slingbox from their own account on Slingbox.com. Just remember that the Slingbox can only provide one stream at a time!
Here is an article which describes the process of adding a guest user:
Hope that helps!
The Sling Moderation Team