If you are concerned about security, it might be a good idea to upgrade to 6.7, as there have been a number of security fixes since 5.x series.
Personally, on my forums, I use the same method here at UBBCentral. IP Addresses are logged, but only Admins and Mods can see them. I don't like the idea of visible IP addresses because dishonest people can use that information to their advantage, or try to exploit/DOS a user that cheeses them off.
