SpiderOak share rooms are not indexable or crawlable by search engines. This means no one will ever see your share room in Google search results. In order to access a Share Room, you must be able to type in the exact URL or enter the ShareID and RoomKey. In this case, the RoomKey itself works as a password.
However, due to popular demand we are in the process of adding the option to ask for a password when accessing a share room. We will update our website and blog when this feature is available.