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I think saying people "should be" using nofollow is a bit strong. More like people can use it for internal links if they're power-user-y enough to want to sculpt PageRank flow within their site at the link level. But I'd say that most regular webmasters don't need to worry about link-level PageRank flow within their site. I think saying "power users and webmasters should be employing on their sites" overstates it a little. It's available if you want to get into that much fine-grained control.