I think the entire purpose of having a login system is to show different things (in some way - links, content, ability to engage in something, etc.) than to people who aren't, so any type of login could probably be considered cloaking if we 'push it to the extreme', but that would be silly ... GoogleBot's not logged in while visiting and their visitors (unless they're already members and surf logged in to your site) see exactly the same thing when they visit initiall, so there's no cloaking there in my opinion.
Out of sheer curiosity...
we know that visitor left this page and went to that site but we don't see a link for that site, hmmm
How do you think their Search Algorithm would know?