What’s it take to tip over an island?

If you add lots of people to a large island, will that island tip over? US Congressman Hank Johnson raised the question, and then debated himself, in an official hearing in May 2010. (Thanks to investigator Sarah Constantine for bringing this to our attention.) The island in question is Guam. This video documents the self-debate:

BONUS: There are many news reports about this. Here’s one by CBS.