My opinion, no publicly facing messaging system should allow anyone except an account owner to post on their behalf. That is a HUGE privacy concern and could be career ending for some people. Can you imagine if someone went on there and started posting a bunch of negative things about your workplace under your account? Or started posting a lot of inaccurate information about what you specialize in under your account? Or goes on and posts racist or hateful things on there? the list goes on and on.
it is incredibly scary to think that the admins on twitter could selectively pick and choose people to post on their behalf and destroy someones career.
Hopefully this hack will make twitter think twice about what they are capable of from their admin panels and work to reduce the appeal for hackers to get access to it.