http://dev.riseup.net/privacy/syslog-ng-anon/ contains a patch to add some privacy options to syslog (filter ips etc.) I think this is a good thing, especially as we in germany currently have some legal issues about ip logging. I'd suggest to add this to the syslog-ng ebuild. If you don't wanna enable it by default, some local useflag like anon will do fine I think.
*** This bug has been marked as a duplicate of bug 117593 ***