variable lost when while loop piped

[ecashin]

Configuration Information [Automatically generated, do not change]:
Machine: i686
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i686' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/local/share/locale' -DPACKAGE='bash' 
-DSHELL -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -g -O2
uname output: Linux kokone 2.6.15.1 #8 SMP Thu Feb 15 15:39:10 EST 2007 i686 
GNU/Linux
Machine Type: i686-pc-linux-gnu

Bash Version: 3.2
Patch Level: 0
Release Status: release

Description:
        A variable set inside a while loop loses its value if
        the while loop is piped to a command, e.g., sed.

Repeat-By:
        ecashin@kokone ~$ seq 0 9 | ~/build/bash-3.2/bash -c 'while read a; do 
last=$a; done | cat; echo :$last:'
        ::
        ecashin@kokone ~$ seq 0 9 | ~/build/bash-3.2/bash -c 'while read a; do 
last=$a; done; echo :$last:'
        :9: