What is the difference between Viral and Viral Premium? 

Viral and Viral Premium are identical except:

• Viral premium offers CNAME which is a feature of your DNS at your domain registrar where you can point a domain or subdomain to Nanacast to cloak a Nanacast hosted membership area to look like its hosted on your domain. It also offers a slight bit more customization in some areas of the system.
• Viral premium also offers a "staff" feature where you can create a free membership and on your Nanacast profile select it as your staff membership. Once you do that you can add members to that membership and those members will have limited access to your account to manage transaction customer service like refunds, voids, cancellations etc. and client access customer service etc. Staff do not have access to your profile and cannot manage content.

Other than that, all the features of both account levels are listed on this page: 

http://nanacast.com/docs/features

Keywords: Viral Premium, features