Pflogd

 # ps auwx | grep pflog
   root          19229  0.0  0.3  5016  1432  ??  Is   10:56AM   0:00.01 pflogd: [priv] (pflogd)
_pflogd       19230  0.0  0.3  5080  1464  ??  S    10:56AM   0:00.06 pflogd: [suspended] -s 116 -f /var/log/pflog (pflogd)

As you can see, I had pflogd suspended for some reason.

from pflogd(8):

    pflogd tries to preserve the integrity of the log file against I/O
    errors.  Furthermore, integrity of an existing log file is verified
    before appending.  If there is an invalid log file or an I/O error, log-
    ging is suspended until a SIGHUP or a SIGALRM is received.

I tried

  # pkill -HUP pflogd

but no luck, it was still suspended.

 # /etc/rc.d/pflog stop
 # mv /var/log/pflog /var/log/pflog.fscked
 # touch /var/log/pflog
 # chmod 600 /var/log/pflog
 # /etc/rc.d/pflog start

and I was back in the running:

# ps auwx | grep pflog
root          19406  0.0  0.3  5016  1432  ??  Is   11:07AM   0:00.01 pflogd: [priv] (pflogd)
_pflogd       19407  0.0  0.3  5080  1456  ??  S    11:07AM   0:00.03 pflogd: [running] -s 116 -f /var/log/pflog (pflogd)