DId you happen to make sure that the album was still being shared? If you had sent others a link to your album and then happen to unshare and then re-shared out the album, the link will change. The other person would see this screen shot. I explain this in detail in our faq post "How do I share my photos in Revel" http://forums.adobe.com/thread/1157995?tstart=0
As long as the link is valid and you can copy the link into a browser to view the album, then you can send it to anyone that you want. You can select to turn off "Allow downloads" to restrict users from downloading your images.
Let me know if you have any other questions regarding Revel