Cityspeak Turns Billboards Over To Text Messagers

From Art Threat:

Cityspeak is ephemeral graffiti, using private modes of communication to generate public displays of commentary about a particular location. It is an example p2P (private-to-public) communication which allows participants to use communication technologies we tend to think of as private--cell phones and Personal Digital Assistants--to create public displays.

Cityspeak's website also allows anyone to post a message to the billboard. [Link]