What should you share?
You are encouraged to share maps, data, and applications if they are useful to others and viewable in a web browser, a mobile device, or desktop viewer. For example, you might want to share a map that shows your local watershed system or a utility network of your county. You might also want to share a Flex code sample you think would be useful to other Flex developers. Finally, if you are an ArcGIS user, you might want to share your cartography and data through a layer package file.
Some content is appropriate to add but is not appropriate to share with people outside your organization. Such private content includes maps that are works in progress and proprietary or business-sensitive data. With works in progress, you probably want to share the content only to your organization or even just a group within your organization that is involved with validating and fine-tuning the information. Once the content is finalized, you can then share it with everybody (in other words, make it public). In the cases of proprietary and business-sensitive data, you will probably always want the content to be private.
By default, content you add to ArcGIS Online is only accessible to you. Your maps, apps, and data are not available to others—for example, they do not appear in search results and aren't part of any group—unless you enable sharing on the item.
If you want to share your content, you can share it with your organization, groups you belong to, or everybody (public). You can also share it with a combination of groups, your organization, and everybody. If you make an item public, it is accessible by everyone including anonymous users using an ArcGIS Online client such as the ArcGIS.com website and map viewer, ArcGIS apps, and custom applications. Access to items shared only with a private group requires that you have shared the item with that group and that group members are logged in. This is enforced anytime the item is accessed.
Esri secures all access to your information. User identity is established through a login process that always takes place over HTTPS. Subsequent access to information requires authentication tokens acquired at login time and takes place over HTTP.
Administrators have the option of enabling additional security on their organization in which case all access to information takes place over HTTPS (SSL). See Securing hosted services for more information.
Your organization may restrict members from sharing items outside the organization. If this is the case, users and publishers won't see options to share content or groups with everybody (public). Administrators, however, can choose to share any item in the organization publicly.
Sharing with a public account
If you have a public account, you can add items to ArcGIS Online, create public groups, and share your items with everybody and with the public groups you belong to. You can also access any item shared with everybody (public) and join public groups owned by other public accounts. You cannot create or join private groups and cannot join groups owned by an organization or invite organizational accounts to join your groups. An item you want to share to a group needs to also be shared with everybody (public). Any existing private groups or items shared privately to groups will remain private; ArcGIS Online will not make public any existing private groups or privately shared items.