"Something meaningful shocked the eCommerce ecosystem in January," writes Stifel's Jordan Rohan in his contrarian note on Google (GOOG -1.2%). Search engine marketing (SEM) firm IgnitionOne saw a 9% Y/Y drop in ad spend in Jan., followed by subdued growth of 9% in Feb. and 11% in March. Rohan, who also reports hearing Jan. mobile banner ad buying was weak (a negative for MM), does admit other SEMs saw mid-teens growth, but points out Google shares have little margin for error. "Google replaced Apple in tech portfolios as the comfort food trade in mobile..." AMZN +1.5%. EBAY -1.7%.