Quite possibly this isn't a hack and someone got a Twitter admin's account, then got access to the admin panel and "all" accounts without having to hack much of anything.
If there is such a level of privilege in Twitter's stack, that says a great deal about their technology. Insiders must not be able to act as users except in prescribed ways requiring two-person control, logged and 100% audited. Glass-breaking privilege escalation should set off every pager in the company.
