In researching digital graffiti, the most prominant artists on the scene are from a group called The Graffiti Research Lab.  This group was founded by Evan Roth and James Powderly during their fellowships at the Eyebeam OpenLab.  Evan Roth comes from the backgrounds of Architecture and Communication Design.  He currently teaches couses at Parsons School of Design.  James Powderly studied both music composition and interactive technology.  These two met in New York working for the digital artists collective, Eyebeam Openlab.  They began developing different ideas and tools for artists wishing to take graffiti to another level.  A relatively simple form of digital graffiti was introduced by the two called LED throwies.  How to make these can be found on the instructables website.  The throwies consist of a LED, a small watch battery, and either an adhesive or a magnet.  The idea is to place these lights in urban areas to make a pleasing colorful on an otherwise ugly surface.  Some have even made tags out of these lights in the idea of the Light Bright.

There have been several controversies over these throwies.  First, it is seen as graffiti even though it is not as permanant as paint.  People argue that it defaces buildings.  Another concern is that if not disposed of properly, the lithium batteries could leak and contaminate the soil and water.  This is concern that has been addressed by members of the GRL as well as bloggers interested in the throwies.  The battery should do a miniscule amount of damage compared to electronic objects and toys that are purchased to be disposed of.

http://www.10zenmonkeys.com/2007/11/15/catching-up-with-an-aqua-teen-terrorist/

All of the ideas expressed by GRL maintain a sense of outsider synicism and freedom in this digital age.  Their codes are all open source and their plan is to give everyone an opportinity to change their environment.  Several other GRLs have been established in countries such as Mexico and the Netherlands.  These groups work as a collaborative, but also independantly -- a loosly based group.

http://www.youtube.com/watch?v=isfrCIhQ5HE