NOTE: Information listed here is good as of 3/6/2015 and is subject to change.
There has been confusion with the new Power BI Public Preview and Sharing. Currently, the only item that can be shared is the Dashboard.
People have asked if they can just share with anyone. The answer is no. You can only share with people that are within your Organization/Tenant. So, any domain that is registered within the tenant.
For example, I have the following domains registered with my tenant:
That user will then get an email with a link indicating the dashboard has been shared with them. If I go to share the dashboard with someone not in the domains that are active in my tenant, I won’t be able to share. For example, email@example.com. Battlestar.local isn’t a valid domain within my Tenant. Or the internet for that matter.
One or more e-mail addresses are outside your organization: battlestar.local