When using 'preupgrade' (in my case from f7 to f9 and then f9 to f10), you note that your logging will die. The /var/log/messages and /var/log/secure will just remain empty.
It appears the issue is that the logging system changed sometime after f7, and there's a weird dependency-inconstency that prevents removal of the old logging system, prior to installing the new one. I noticed this after seeing a new daemon 'rsyslog' on fresh-installed fedora 10 systems that didn't occur on the upgraded ones. I believe you'll know you have this issue if you do "chkconfig --list | grep log" and nothing comes up.
Here's what I believe i had to do, on two systems, to re-enable logging after upgrade. Warning, brute-force is involved, comments appreciated:

golem-136-~> sudo yum install rsyslog
Loaded plugins: fastestmirror, refresh-packagekit
Loading mirror speeds from cached hostfile
Setting up Install Process
Parsing package install arguments
Resolving Dependencies
--> Running transaction check
-> Package rsyslog.x86_64 0:3.21.9-1.fc10 set to be updated
> Processing Conflict: sysklogd conflicts rsyslog
--> Finished Dependency Resolution
sysklogd-1.5-5.fc10.x86_64 from installed has depsolving problems
  --> sysklogd conflicts with rsyslog
Error: sysklogd conflicts with rsyslog

golem-137-~> sudo yum remove sysklogd
NOTE: This uninstalls >700 packages:  don't do it!

golem-137-~> sudo rpm -e sysklogd
error: Failed dependencies:
        syslog is needed by (installed) initscripts-8.86-1.x86_64
        syslog is needed by (installed) cronie-1.2-7.fc10.x86_64

golem-138-~> sudo rpm -e --nodeps sysklogd
error reading information on service syslog: No such file or directory

After reboot, note that the proper behavior of logs happens again!! ('messages' and 'secure' were both 0-length prior to the fix):

  /var/log:
  total 3716
  drwxr-xr-x 17 root    root       4096 2009-01-15 10:49 ./
  -rw---  1 root    root      42080 2009-01-15 10:41 messages
  -rw---  1 root    root       1007 2009-01-15 10:38 secure
 ...
  -rw---  1 root    root          0 2009-01-04 04:02 messages-20090111
  -rw---  1 root    root          0 2009-01-04 04:02 secure-20090111