One disadvantage of social media marketing is the low success rate of content going viral. A lot of the sharable content that is generated will not go viral, but the one piece of content that does go viral will pay for itself ten times over. Social media marketing is very time intensive. It requires a significant time investment to create the shareable content to be distributed; and review the analytics on each piece of content that is distributed.
I wish I could help you, but I'm not very competent at such questions. When it comes to marketing, I prefer turning to the marketers from http://thecmoclub.com/ community. These guys always offer great marketing ideas! So, you can contact them too!