A report from Forrester Research and GSI Commerce illustrates the fact that social media has little to no effect on purchasing power.
I've often thought this was the case and that people were far more inclined like myself to follow results from search engines and newsletters I get especially reghardware for example, but that might show a bit about what types of things I purchase.
I like to make up my own opinion and with what I know about Social Media I rarely trust what I see. What I can obtain myself through searching the web I trust more but not fully.
Having seen among the people I know, who are so called Social Media experts or gurus (for the others I don't know, don't take this personally) I wouldn't trust them one bit to help a company truthfully promote their product nor do it in an efficient way.