Yes, if you use a weak seed on a service like brainwallet to deterministically generate your keypair then it is quite easy to brute force / dictionary attack yo

Yes, if you use a weak seed on a service like brainwallet to deterministically generate your keypair then it is quite easy to brute force / dictionary attack your private key. This is why clients like Electrum force you to use a long passphrase that they themselves generate. This really isn't new or novel. Side note: I ran this attack months ago and you would be shocked at how many weak passphrases actually had money in them at some point.