SUNNYVALE, Calif.—The last quarter of 2010 ended a strong year for the digital marketing industry with substantial growth overall and in the key sectors of finance, auto, retail and travel. Search engine marketing (SEM) posted solid year on year (YoY) growth of 23% and 18% quarter on quarter (QoQ). This is according to Efficient Frontier, a leading performance marketing company managing more than $1 billion in marketing spend....