Here in the U.S. past legal battles have pretty much established that search rankings are a matter of free speech. Otherwise, we'd have probably seen a lot more search rankings-related lawsuits by now (though it hasn't stopped complaints about how Google shows its own content in search results).
Still, the topic has come up yet again. A blogger, who goes by the name of Fogus, got some discussion going on Twitter:
@fogus strike while the iron is hot!
He then blogged about the tweet, adding, "After tweeting I thought a little deeper and came to fear the possibilities."
He mentions the ordeal currently facing The Oatmeal, in which it is being threatened with a suit by what he calls "a content bottom-feeder".
On the search engine side, there's been a couple of solid court decisions in the United States:
- In SearchKing vs. Google, a company sued because it didn't like its rankings/PageRank. SearchKing had been selling links that passed PageRank, which violates Google's quality guidelines. The court determined that "PageRanks are opinions - opinions of the significance of particular web sites as they correspond to a search query. Other search engines express different opinions, as each search engine's method of determining relative significance is unique. The Court simply finds there is no conceivable way to prove that the relative significance assigned to a given web site is false." As a result, Google was entitled to "full constitutional protection" for its opinions.
- In KinderStart.com vs. Google, a company sued Google over a lower ranking. The judge not only dismissed that case, he allowed sanctions against KinderStart's counsel for making various claims (like Google skewing results for political/religious reasons) that couldn't be proven. So in the U.S., we have a couple very nice court cases that establish that search engine rankings are opinions and protected speech. If someone tried to sue over a set of search results, I believe they would find that a very hard case to make.
Of course, things like libel and defamation apply online as well as offline.