pw keeps setting /etc/group to 0600

/etc/group is supposed to be world-reable, right?  Tools like groups or pw
groupshow certainly seem to think so:

[rstone_at_rstone-server ~]groups
1001 920
[rstone_at_rstone-server ~]ls -l /etc/group
-rw-------  1 root  0  482 Nov 14 21:02 /etc/group
[rstone_at_rstone-server ~]sudo chmod a+r /etc/group
Password:
[rstone_at_rstone-server ~]groups
rstone vboxusers
[rstone_at_rstone-server ~]sudo pw groupadd foo
[rstone_at_rstone-server ~]ls -l /etc/group
-rw-------  1 root  0  494 Nov 17 10:19 /etc/group
[rstone_at_rstone-server ~]

I'm not sure what caused the regression.  I've been seeing the problem
since I first installed -CURRENT on the machine a couple of weeks ago.