Here's how billing works with Placemark.
You pay monthly by people in an organization. When you sign up, you get a default organization. Single member organizations pay for that one member.
You can add as many people as you want to your organization to use it with your company or group, and you'll pay for the users in that group.
When a new person is invited to an organization and they don't have an existing Placemark account, their first organization will be the one they're invited to - so they don't have to set up billing and other information.
If you're removed from your last organization, the next time you log in, Placemark will ask you to create a new organization.