[firefoxd]

They are spamming other websites with links to my website like in your example. Google crawl those other websites, follow the spammy link to mine, and I get penalized for having a page with spam content.

The solution is to tell the crawler that my search page shouldn't be indexed. This can be done with the robots meta tags.

[Goofy_Coyote]

I see, thanks for helping me understand the issue (and also the solution)