Challenged by ROI requirements but bolstered by social media marketing, the search engine marketing industry is predicted to grow by $2 billion in 2010 Search engine marketing in North America already is valued at $14.6 billion, but a new report from the non-profit Search Engine Marketing Professional Organization  ( SEMPO ) estimates the industry will grow 14 percent to $16.6 billion in 2010. The report determined that the industry's biggest challenge was ROI,