No, I don't think so.

They have so many links from various sources that any effort at generating enough "bad links" would be virtually unnoticeable. Other than that, they don't care about their rankings. I mean, would you go to google.com (or bing.com) to find a search engine by typing "search engine"?

You can have a few laughs by doing a google bomb, but that's it. You can't hurt google with negative SEO.