tedster - 9:40 pm on Sep 29, 2011 (gmt 0)
As g1smd mentioned, today Google has more safeguards in place to avoid indexing those 200 status pages that are actually "not found" massages. In the past, when there was a 200 status then every backlink to a duff URL did result in that URL getting indexed - and the widespread "error text" then registered as duplicate content. It can still happen today, though it is no longer nearly so common.
That's why the status code is so important, especially for those who use a custom error message, which is where this problem used to creep in so frequently and easily.