In your business account, you can now configure each application to either share data amongst all users of the business account, or else restrict access to only the owner of the data. For example in Workspaces, if the setting is Private, a user can only see Posts that he has created. In Business Contacts, or Tasks, or Projects, a user can only see contacts or tasks or projects that have the owner field set to this user.
By default, data is shared for all applications. You can change these settings from the Manage Apps section of your web account. Click on the Sharing tab, and choose for each app whether the data is Shared or Private.
Note that users who are administrators can always see everyone’s data, even when the setting is Private. In the web account, Private data is marked by a red label at the top right of the toolbar, when viewing or editing an item.