When I share photos with someone, do they have access to my account and other Albums?

No. When you share an Album with a friend, only that specific Album can be seen by your friend. The Album is viewed in your friend's own password-protected account on the ZoomIn site. The only person with access to your account is you. Your friends create their own accounts by typing in their email addresses and selecting usernames and passwords. From their accounts, they will have viewing privileges only for the Albums you shared with them, and any Albums that they create themselves.