The toll is now more than 12 btc although new transactions have now stopped coming and the person responsible have already emptied the wallet. This can be the biggest blunder on Twitter's side as this can't be caused by a single person screwing up, then only a single account would have posted this endorsement. I guess the Twitter database have been leaked and for now the hacker group is only targeting the verified accounts for maximum earnings possible.
Twitter is hevaily liable on this matter. If they were to switch to a decentralized micro-blogging platform where private keys are the only method to access, this wouldn’t have happened!
This can be a good alternative, but in case of leak of private key there won't be recovery possible and I don't think that one will be able to recover that account from the control of hacker and also wouldn't be able to block the attacker from accessing the account since login only uses private key of the user.