Streaming Replication and archiving

I've been having a look at this, one master + one replica and also one
master + 2 replicas. I gotta say this is a nice piece of functionality
(particularly the multiple replicas).

I've been using the wiki page
(http://wiki.postgresql.org/wiki/Streaming_Replication) as a guide, and
I notice that it recommends the master (and replicas) have a non-trivial
archive_command even after the backup step is completed. ISTM that after
the backup the master's archive_command can be set to '' or '/bin/true'
as the walsender does not make any use of the WAL archive (AFAICS
anyway). Clearly it might be desirable to have the archived segments
around for other reasons - but equally it might be desirable *not* to
have to have to (e.g disk space), or am I overlooking something?

Cheers

Mark