Barry Welford spotted Google showing Google Blog Search results at the bottom of Google web search results. He posted a screen capture at Cre8asite Forums showing this in action. Here is that screen capture downsized a bit.
I have ton some tracking to see if this was tested or seen before. It appears this site spotted and posted on this behavior back on November 23rd, 2006. But we have yet to see this since, as far as I remember.
Forum discussion at Cre8asite Forums.