How private are the letters and albums?
From what we have observed, users of FromABirdie tend to write thoughtful, careful, and personal letters, which makes them quite private. We ensure that only the intended recipient will have access to them (e.g. by password-protecting the album).
People who contribute to the album are NOT able to see each other's letters, although at the end of the process we may share the names of those who wrote with everyone, to enhance the communal experience that these albums are (the organizer has an option to turn this off and NOT share the names of contributors.).
Once a phyisical book is printed we can no longer protect the privacy of the letters, of course. There are also (many) cases in which the book is shipped to the organizer of the book, so they can give it as a present at a party or ceremony. We ask them to respect the writers' privacy, but again have no control over it.
Finally, there are cases in which the creator of the album wants to have complete editorial control, for example to ensure that the final book is perfect. We do let creators see all the letters, but we ask them to let writers know that that will the case. We have never had a single issue or complaint with that.
In summary: while the letters are not really fully private, since the creators may choose to see them and they may be printed in a physical book, they are also not intented to be public either. People tend to write honestly and to address the recipient directly (rather that feeling that they are posting on public channels), but they also knowing that the letters may be seen by others.