Just putting myself into Google's place - if I was concerned with quality original content, isn't the easiest thing to do just to check whether a blog has the autoblog, wp-o-matic etc plugins installed. If yes, then a good chance that the content isn't original and so either very low ranking or simply not indexed. If this is the case, can/should plugins be hidden? I know that robots.txt is ignored by Google so that isn't much help. Forgive me if this is answered elsewhere - not sure what to type into search to find an answer.