When I had the site for upIRC (my first product) hosted on my own server, I had a speech on there about shareware registration vs. cracking. When I built and launched the new site, I left that out. I put it back in there as a result of the game being cracked, and the same effect shows... people search for cracks for my software and end up visiting my site. How funny is that!
This generally happens with Google (which, incidentally, generates most of my search engine hits). I believe it's happening because my site's page rank with Google puts it at the top of the list for the search terms which, for my own software, it should :-)