I don’t know about whether Google links never appear in Google Webmaster Tools. I think I have had, like I think the Google blog has me on the blog roll or something, so I’ve seen some links from Google.
You know, if we have search results that are not blocked by robots.txt, people find out, notice, and let us know, and, you know, blog about it, and it drives a lot of attention. So, we try to be relatively careful. You know, things like search result don’t flow page rank within Google, most Google properties, we try to make sure that they’re not too spamable, and if we’re worried that something might be potentially abused, then often will use a nofollow attribute.
For example, I think Google Knol, most of the external links started out as nofollow, but then over time as we learn which Knol authors were more trustworthy, we lifted the nofollow on those Knol authors. So, certainly, we do sometimes flow page rank, but we try to be relatively careful because we’re mindful of the people that do try to abuse it.
by Matt Cutts - Google's Head of Search Quality Team