as per http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=304242

man5/hosts.5

@@ -37,7 +37,7 @@ with hostnames, one line per IP address. For each host a single
 line should be present with the following information:
 .RS
 .PP
-IP_address canonical_hostname aliases
+IP_address canonical_hostname [aliases...]
 .RE
 .PP
 Fields of the entry are separated by any number of blanks and/or
@@ -45,10 +45,9 @@ tab characters. Text from a "#" character until the end of the line is
 a comment, and is ignored.  Host names may contain only alphanumeric
 characters, minus signs ("-"), and periods (".").  They must begin with an
 alphabetic character and end with an alphanumeric character.
-Aliases provide for name changes, alternate spellings,
+Optional aliases provide for name changes, alternate spellings,
 shorter hostnames, or generic hostnames (for example,
 .IR localhost ).
-The format of the host table is described in RFC 952. 
 .PP
 The Berkeley Internet Name Domain (BIND) Server implements the
 Internet name server for UNIX systems. It augments or replaces the
@@ -80,10 +79,16 @@ advantage.
  127.0.0.1       localhost
  192.168.1.10    foo.mydomain.org	foo
  192.168.1.13    bar.mydomain.org	bar
- 216.234.231.5   master.debian.org      master
- 205.230.163.103 www.opensource.org
+ 146.82.138.7    master.debian.org      master
+ 209.237.226.90  www.opensource.org
 .fi
-.SH "HISTORICAL NOTE"
+.SH "NOTE"
+Modifications to this file normally take effect immediately,
+except in cases where the file is cached by applications.
+.SH "HISTORICAL NOTES"
+RFC 952 gave the original format for the host table, though it has
+since changed.
+
 Before the advent of DNS, the host table was the only way of resolving
 hostnames on the fledgling Internet. Indeed, this file could be
 created from the official host data base maintained at the Network