Interesting... further investigation shows two things:
1) The outgoing connection is triggered on an interval and not related to the page you are viewing. After a set interval, a new list of known-bad domains is downloaded. User information is not sent to Google regarding the page you are visiting.
2) This is not part of the toolbar. The download of TrustRank data is a feature built into the Firefox web browser as a phishing filter.

Still, interesting.

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The best way to learn anything, is to question everything.