Hi, starting June 28 you can subscribe to ArcGIS Online for the exact number of Named Users you need for your organization - no minimum number required for a subscription. The only constraint is that you must have at least one (1) Level 2 Named User to be the administrator of the subscription. After that, you can have as many (or as few) Named Users (Level 1 or Level 2) as you want - no matter how small or large your organization may be.
Got a small business and need 1 administrator/author and 4 viewers? No problem – buy one Level 2 Named User and four Level 1 Named Users. Got a really small business and only need one Named User to make maps for a website? No problem, buy a Level 2 Named User.