The first time I run HijackThis, I can mark a bunch of the settings to be ignored on all future runs. When I use HijackThis at work, I want to be able to copy that ignore file to other computers - there's a lot of overlap, and whatever settings are confirmed safe on one computer are safe on another, too. So, where does HijackThis store its ignore list? I haven't noticed a file in my user directory, or found it in the registry.
I'm only speculating here, but I have to believe that regardless of where this information is stored it must be done using a fairly strong encryption method using a per-machine key, making automatic deployment of your whitelist impossible. Otherwise, a malware program could easily just add itself to the list or overwrite an existing list with it's own, and HijackThis would become worthless.