Going back to the orginal question: It is now my understanding that percentage of debt compared to total available credit IS a factor that can reduce your score. The more UNUSED credit you have, the higher your score. My credit score tools at creditexpert.com confirm this. If this is true, cancelling your unused lines of credit can lower your score since it increases your debt/available ratio.

Of course, at some point being over exposed and having too many lines of credit at some point will hurt your score.