One person posted a rant in the Google Webmaster Help forums about the "Top Contributors / Bionic Posters" in that forum. In short, Top Contributors / Bionic Posters are given the title by Googlers, who believe that these people are smart enough, experienced enough, skilled enough and helpful enough to be giving answered at Googler levels. But this person felt the Top Contributors / Bionic Posters were not helpful.
The interesting part of this thread is that Googler, JohnMu, does the right thing and backs up the Top Contributors / Bionic Posters with a really nice post. The post, kind of leads me to see that Google may (maybe stretching it here) consider the Top Contributors / Bionic Posters as "certified Google SEOs," if there is such a thing. Google does have certified AdWords professionals, Ad Manager pros, Google Apps, etc, but not Google SEOs, simply because it is something that would be considered very controversial on many levels. But in a sense, these Top Contributors / Bionic Posters are Google Certified SEOs.
Read John's post:
This is one of the reasons we mark a few people as Top Contributor / Bionic Poster. It's not because of their own website(s). Some websites rank high for no particular reasons and some websites are filled with information that is made up -- I wouldn't trust people online just because of a website that they give you :).
Top Contributors / Bionic Posters are people who do more than just work on a single website. They help thousands of users here with their problems. They see issues here weekly which the average webmaster does not ever see. Because of that, they're frequently very quick in finding a diagnosis and frequently the diagnosis is spookily correct (not always, I don't think that's really possible). They might be a little too direct at times, but when you have so many people lined up asking for help I don't think it makes sense to be anything else than direct. Sometimes things can get heated, they're only people after all :), but overall they help an awesome amount of users.
Keep in mind that you can't become a Top Contributor / Bionic Poster by just posting a lot of stuff here. It's not based only on the quantity but to a large part on the quality of the feedback given. When we find that someone is doing an exceptional job here, we may decide to reach out to them and ask them to become a Top Contributor / Bionic Poster. We don't do that based on a single reply, we do that by looking at 100s and often 1000s of replies to webmasters with all kinds of problems.
If this message is not a clear indication that Google vouches for the Top Contributors / Bionic Posters, then I don't know what is. I don't blame JohnMu for backing up the Top Contributor / Bionic Posters, but it also leads John and Google to basically certifying them as certified SEOs, which can get hairy.
Forum discussion at Google Webmaster Help.