Since version 4.x, the logrotate package has erronously been rotating
/var/log/lastlog. This file does not need to be rotated. It is a file
of records of last login times, indexed by UID. It only grows with the
addition of new users. By rotating (and erasing) this file, users' last
login time and location are forgotten each month. The solution is to
remove the section for lastlog from /etc/logrotate.conf.
Note that if there is a large gap of unused UIDs, this file may seem
larger than it really is (as it will be a sparse file). Use
'du /var/log/lastlog' to determine its actual usage.
If there is some other reason for this file being rotated, I would be
interested in seeing that reasoning.
Fixed for logrotate 3.3.2 -- thanks for the report.