Purpose of having multi listener ?

[KenEwald]

(ADDRESS = (PROTOCOL = TCP)(HOST = 192.9.100.1)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.9.100.2)(PORT = 1521))

Correct me if I'm wrong, but isn't the address list (above) for using 2 network cards (each with it's own IP) in 1 server?

Or failover for a RAC environment...

From "Enhanced Service Accessibility with Multiple Listeners" link above:
"For some configurations, such as Oracle9i Real Application Clusters, multiple listeners on multiple nodes can be configured to handle client connection requests for the same database service. In the following example, sales.us.acme.com can connect to sales.us.acme.com using listeners on either sales1-server or sales2-server."

(DESCRIPTION=
(ADDRESS_LIST=
(ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521))
(ADDRESS=(PROTOCOL=tcp)(HOST=sales2-server)(PORT=1521)))
(CONNECT_DATA=
(SERVICE_NAME=sales.us.acme.com)))

Sorry, but I'm confused.