If one REALLY wants to be able to share a file privately without giving away personal credentials, there is a way.
There is a Chrome extension called miniLock. What each person does, is install the extension. It will ask you for an email address and a passphrase. The extension generates a public encryption key. This key is called your miniLock ID. You can share your miniLock ID with anyone. Put it in your email signature, whatever. When someone wants to share a file with you, they drop the file on the app and adds the recipients miniLock ID to it. This creates an encrypted file that can be shared publically through DropBox, Google Drive, or whatever. The recipient drops the file on the app and it decrypts it with the private key.
Boom.
Having said that, the point of the forum is to share. 
Mark W.