I didn't get into business for this!

I don't want to derail this discussion but think I should probably explain what I said above a little further. First though, I can say without a shadow of a doubt and from painful experiences, that yes, you can take down someone else's site in Google with enough bad links. However, the more authoritative it is the harder it is. In fact, you can even do this by pointing enough "good" links to someone's site.

Anyone who believes Matt Cutts when he says: "What others do to your site can't hurt you." has either never met him, or is just plain naive IMO.

In my example above it was actually partly my own fault that this happened though.

I didn't have my server correctly set-up (just like millions of other websites), so when someone entered a non-existent/made up URL on my domain the server showed that URL but with the content from my index page. This is a really bad idea even if no one is trying to harm you since Google is likely to index loads of pages that don't even exist as being duplicate content of your index page. In my case it was made even worse by the fact that the links were pointing to non-existent URLs that my competitor had made up, with some horrible pornographic words in them. So Googlebot figured that I had loads of these horrible file names with words that was triggering the safe search filter, and those pages were all duplicates of my index page....expensive lesson learned!

I have learned something else as well though, and that was what got me through that bad time. Karma is a bitch for those who intentionally hurt others.