The idea that somebody working for the government that has an opinion should naturally be given any kind of voice whatsoever is ridiculous. If it's not part of their job they need to be fired immediately.
From youtube streams of meetings to twitter and facebook posts of government news (ex. weather/disaster alerts, public health issues, traffic accidents, voting date reminders) to vimeo uploads of police body camera footage.
The amount of easy transparency and important information delivered directly to citizens in a way they can choose to engage with is a big step in the right direction.
Before you basically had some traditional media (ex. radio/newspaper/nightly news) or you were required to have the free time to attend government functions yourself.
You might say "Then why not use official websites?" but there are many thousands of government websites for each agency/department/committee/public figure and while they have very useful information they are not good at what social media does.
Communicating with the public can be part of their job. In some cases they write and send tweets themselves. In other cases they might have a whole team handling their social media.