Forgot crypto, my actual bank account and retirement accounts and nest egg are accessible online these days. The login credentials for those are stored somewhere so I really hope they don't invent brain hacking technology to steal those. If you're the type to use a password manager, then I'd say those are the most valuable pieces of data you store. 2FA isn't never going to be totally utterly 100% foolproof so I wouldn't count on it solely to protect what I have.
> The login credentials for those are stored somewhere
Most password are not stored on any server. Instead, a hash of the password and possibly a salt is stored. Stealing those hashes is only a problem for weak passwords that can be brute forced.
I'm talking about on the user side, not the server's side.
I think personal content like photos of you/your family growing up, projects and works stories you created for school, old music that doesn't exist anymore or a particular track that is impossible to find because it was never digitized.
By definition, these things can't really be reproduced or replaced and they have the abillity to help you travel back in time and know yourself better
The most valuable data would be the source code for an efficient elliptic curve discrete log (ECDLP) algorithm... if one exists. That would break most cryptography in existence, and allow undetected inflation of confidential crypto using Pederson commitments.
If you can collect & store large amounts of telemetry data on people (online habits of all forms) you could make ridiculous amounts of money. The trick is getting the data, I suppose. I am not sure how to do that.