Are the search engines taking on the challenge of incorporating social media into their rankings? Likes, retweets and shares are significant factors in any web site's popularity. But looking at the search engines in general, they seem to be behind the pack somewhat on this front. Social signals are very important - but not every post is the view of one individual. It may be a commercial entity posting many hundreds of similar or identical comments through a bot of some kind.
Another point is that people can drum up business at the expense of their rivals who have great websites and have done everything within the rules when it comes to SEO. The fact is, if anyone can quite easily set up a YouTube account or blog account, then anyone can quite easily attempt to flame others with comments that serve to help them make money by some nefarious means, or attempt to sell products through what amounts to free advertising, by drawing people to those comments. Anyone can express self serving opinions, or post defamatory material that builds one reputation while harming another. These are all negatives when conducting search engine marketing and Google for one has claimed its philosophy to be a profoundly positive one.
People can set up false Twitter accounts or Facebook accounts as a part of their search engine marketing campaign strategy, purporting to be people they are not. Anyone can post anonymous comments on most blog sites - people can often comment on newspaper articles from the comfort of an anonymous desktop or laptop.
It is very easy to spam an FB wall. When it comes to social media, the search engine giants need to behave in an ethical way - much like the mainstream media. They need to ascertain identities, ensure that there aren't bots of any kind behind postings or comments, and make sure that the content that is contained within a link is reliable.