The current hype surrounding advertising on social media sites such as Facebook et al. is doomed to end soon (2013 in fact!). The simple fact is these kinds of sites do offer advertisers a massive engaged audience but social marketing it most certainly aint. Most of it is bog-standard display advertising. A better option is the ability to create fan pages and generate lots of likes... but is this really going to be a solution to get people to buy more product? There seems to be scant evidence of any ROI associated with fan pages (unless someone can tell me different?).
In the near future, the true essence of a social media campaign will be to conceive it as a word of mouth campaign. This is and will always be, the best form of marketing EVER. Up to until now, it was almost impossible to control, measure and stimulate. A new focus on word of mouth marketing using social media sites (or any member site for that matter) could answer that eternal riddle. However, marketing nirvana will never be achievable by just sticking a nice looking ad up or getting some brand likes on Facebook.