L'exemple est réservé

Les domaines example en .com .net et .org sont réservés par l’IANA.

$ whois example.com
Whois Server Version 1.3

Domain names in the .com and .net domains can now be registered  
with many different competing registrars. Go to http://www.internic.net  
for detailed information.  
-snip-  
Domain Name: EXAMPLE.COM  
Registrar: RESERVED-INTERNET ASSIGNED NUMBERS AUTHORITY  
Whois Server: whois.iana.org  
Referral URL: http://res-dom.iana.org  
Name Server: A.IANA-SERVERS.NET  
Name Server: B.IANA-SERVERS.NET  
Status: REGISTRAR-LOCK  
Updated Date: 26-mar-2004  
Creation Date: 14-aug-1995  
Expiration Date: 13-aug-2011  
-snip-  
Registrant:  
Name: Internet Assigned Numbers Authority (IANA)  
Organization: Internet Assigned Numbers Authority (IANA)  
Address1: 4676 Admiralty Way, Suite 330  
Address2:  
Address3:  
City: Marina del Rey  
State/Province: CA  
Country: US  
Postal Code: 92092  
Phone: 310-823-9358  
Fax: 310-823-8649  
Email: res-dom@iana.org  
Registration Date: 11/01/2001  
Last Updated Date: 11/01/2001  
-snip-  

Ceci est décris dans la RFC 2606

[…] To safely satisfy these needs, four domain names are reserved as listed and described below.

.test
.example
.invalid
.localhost

“.example” is recommended for use in documentation or as examples.

Les sites web en question renvoient justement vers la RFC.