ZydoSEO - 3:07 pm on Jan 13, 2013 (gmt 0)
If you're showing Googlebot and non-logged in users the same thing, there should be absolutely no issues. Googlebot is not going to log in so it has no way of knowing that logged in users are being served different content.
However, if you're showing Googlebot one thing and non-logged in users something different this "could" be considered cloaking. I say "could" because it really revolves around your intent for rendering different content.
If you're simply personalizing a user experience based on a cookie you set in a user's browser, their past history on your site, and this results in something slightly different than what Googlebot sees then this should withstand any type of manual review by a Googler. They know that Google is not the only company on the web which does personalization.
However, if you're showing Googlebot one thing in order to rank for some popular keyword phrase (Katy Perry, Britney Spears, etc.) and then serving up something totally different (for example, #*$!) then this is not going to stand up to a manual review. You may go undetected indefinitely, but should you get reported, such a technique will likely result in a penalty.
In regard to hiding ads from Googlebot while showing them to non-logged in users, you might "argue" that this is personalization. But I think hiding such ads is very risky. Google might argue that by doing so, you are trying to manipulate their search results to gain higher rankings and avoid filtering due to one or more of their updates like Above the Fold.