Targeted likes and shares on facebook page will matter on brand credibility, if like and share comes from different areas where the business should be just a local business would give an alarm. Why? Because questions will arise from there, are the likes and shares for real? are they not just spam accounts?and so forth.
It won't really give much on keywords SERP, unless you have good content on your facebook fan page that includes yourr keyword or they are currently active and engaging in your fan page- I was talking about the fans.
Hope this helps.