Le Décodeur.

I've recently read a book by Guy Tournay titled Le Décodeur.
This book pretends to describe a website on a serie called Street Hassle closed by the FBI for being used as a communication channel for terrorist organisations.
Wondering about the reality of the facts on which the book is based, I did a bit of searching, here are the raw results.

Links referenced:

http://www.usatoday.com/life/cyber/tech/2001-02-05-binladen.htm
The article is available. Describes the use of steganography as a communication channel for terrorist organisations. Dated 02/05/2001.
No mention of "Street Hassle" nor of websites closed by the FBI.

http://www.lemonde.fr/article/0,5987,3244--222839-, 00.html
or
http://www.lemonde.fr/article/0,5987,3244--222839-,00.html
This article is no longer available.

http://www.citi.umich.edu/techreports/reports/citi-tr-01-11.pdf
This publication is available, it is a paper about steganography, as a response to the USA today article and a wired article. It is not a report about analysing ebay content as stated in Le Décodeur.

http://linuxfr.org/2001/09/28/5184,0,1,0,1.php3
This web page is no longer available.

http://www-rocq.inria.fr/codes/WCC2003/
This web site is still online, and is effectively the web site of the WCC 2003: International Workshop on Coding and Cryptography, March 24-28, 2003, Versailles (France). The focus of this workshop is related to the activities of the CSIS.

http://www.ina.fr/produits/publications/da/92/index.fr.html
This is a link to the INA: Institut National d'Archive, referencing a book titled Les dossiers de l'audiovisuel with an article by Guy Tournaye titled TV/Internet : convergence ou cannibalisation ? No more information about the article is available.

Other references:

The George Mason University exists : http://www.gmu.edu.
The CSIS exists : http://www.isse.gmu.edu/~csis/.
No publication on FBI or Street Hassle.
No related publication in 2002 nor 2003.

No "street hassle" serie on Imdb.
No results on google for +"street hassle" +abc.
No results on abc.com for Street Hassle.
No results except online librairies and critics for "guy tournay".
"Street hassle" is a Lou Reed album.
.

You can find more information on steganography in the wikipedia.