According to http://www.linuceum.com/Desktop/SocialMedia.php:
Broadcast accounts are things like Twitter, Facebook or Google Buzz, which allow
you to send updates and share things with a number of friends or
followers over the internet. They allow you to keep up with
whatever your friends are doing. Unlike email, broadcasting is more
like a mail shot out to a group of people at the same time. It's not
just text that can be shared, but files, images and video (if your
connection's bandwidth allows)!
Linux has a number of tools to handle broadcast messages, but the
default for Ubuntu is Gwibber. Gwibber allows you to define all your
social media accounts in one place, then to broadcast out across all
of them at the same time. As an example, the next section will show
you how to configure Gwibber with a Google Buzz account (-but the
priciple is the same for the likes of Flickr, Facebook, Twitter, etc).