Currently, AFAICT, LibreOffice needs a username and password to access documents over the network (in my case, an OwnCloud WebDAV connection already negotiated by GVFS). It then uses a master password to protect network passwords.
This is sub-optimal, IMHO. What should be done is to integrate with desktop environment keyrings, should they be available. E.g. if the user is running GNOME, LibreOffice should use gnome-keyring. If the user is running KDE, LO should use KWallet (I believe that's what it's called); if the user is running OS X, use the Apple Keyring. If it's running in an environment with no system keyring, like Windows, LibreOffice should just fall back to the current behavior.
Not sure how possible this is in a cross-platform manner, but seems a worthy goal. I have noticed that initiating LO from the command line under Debian 7 x86_64 + LXDE results in messages like:
WARNING: gnome-keyring:: couldn't connect to: /home/user/.cache/keyring-XxXXxx/pkcs11: No such file or directory
In my case this is likely due to the related gnome package not being installed (and so I have turned these messages off manually). Status set to NEW. Summary amended for clarity. Component set to LibreOffice. Severity set to enhancement.