The higher philosophy behind billboard liberation is the re-appropriation of public space. It is a reaction against the commercialization of the world in which we live where there is a virtual monopoly on the right to broadcast messages into the public sphere. Individuals and organizations (for example the Billboard Liberation Front) carry out acts of adbusting in order to show that culture jamming is a way in which protest is possible.
In a rare example of digital billboard liberation a hacker known as Skullphone has hacked ten of Clear Channel Communications’ digital billboards in Los Angeles. The to achieve this billboard liberation Skullphone had to hack into the Clear Channel network and insert his trademark skullphone between the commercial messages shown on the billboards.
Update: Fresh information suggests that this was not a hack at all but a paid commercial approved by Clear Channel. More information will be presented as soon as it is available.
(via Supertouch who also has more pictures)