A Google Webmaster Help thread has one 'lurker' reporting that an ex-Googler is using spam tactics to both threaten and intentionally hurt his site. By hurt his site, the ex-Googler is allegedly using hacking and injection techniques to push the site out of the Google search results, thus boosting the ranking for his (the alleged ex-Googler) in the Google search results.
This is a bit hard to believe, but who knows - anything is possible. Let me quote the webmaster from the thread, because he makes it sound like he has been around the block and there is nothing he can do.
Around May I discovered another competitors site recent appearance that looked very similar to mine, in fact even the sentences on my homepage were copied directly to his. Then by reading the press release for the company I found out it was started by a high up google employee who quit his job with google to form the company. Shorty after contacting the owner politely introducing myself, I received a threat letter back through email. I don't know if I can publish the email on this site so I will hesitate for now. Basically the owner said he was going to crush me with his skills he had received from google. He then proceeded to tell me if I want traffic on my site that I should buy links. Being a avid reader of the google webmaster forums and faq's I know this is not a good thing to do.
So at the end of all of this my page rank dropped from a two to a zero. And now my site has started showing up on malicious porn sites on the internet and in bad forums, and some seem to be in the form of hidden links that appear to be bought by someone else.
It just seems so hard to believe that anyone, let alone, someone who was employed by Google, would go to these measures. Yes, I know, people do take extreme measures, especially in this area, but a former Googler? The thing is, anyone can pretend to be anyone else on the Internet - emails, names and so on, can be spoofed. So this may be someone using a name in order to threaten and scare this webmaster out of the competition. This wouldn't be the first time Google had impersonators on the webmaster side of the coin.
Hard to know for sure, based on the information I do and do not have.
Forum discussion at Google Webmaster Help.