Thousands of small-business owners have paid marketing firms to get their products and services in front of potential customers on Google, GOOGL -0.39% Yahoo and other Internet search engines.

But a growing number of these advertisers complain about the online marketing firms’ sales tactics and say they made promises that didn’t pan out.

Many of the small businesses’ complaints single out two of the industry’s biggest players: ReachLocal Inc., RLOC +0.29% a publicly traded Woodland Hills, Calif., firm with annual sales of more than $514 million last year, and Yodle Inc. of New York, which generates more than $160 million in annual revenue, according to its website, and is planning an initial public offering.

Some small-business owners rely on Yodle and ReachLocal to manage their Google AdWords accounts. AdWords, the search giant’s largest revenue generator, is effectively an auction for keywords, where advertisers bid to show up near the top of search results for particular terms.

Both Yodle and ReachLocal promise to provide hands-on, personalized support, small-business owners say. ReachLocal relies heavily on software to manage its advertising campaigns, according to four former employees, including two former executives, interviewed by The Wall Street Journal. Yodle also uses automation to make “changes across thousands of accounts at once,” says Jared Slosberg, Yodle’s former chief retention officer.

ReachLocal has about 924 salespeople and manages online-marketing campaigns for nearly 24,000 small and midsize businesses world-wide…Four former employees say its salespeople—who are typically the only point of contact for small-business clients—often aren’t properly trained in the technical skills to troubleshoot or optimize results. The salespeople often don’t check the progress of online-marketing campaigns for smaller clients, the former ReachLocal employees add. (See the rest of this article at: http://online.wsj.com/news/articles/SB10001424052702304626304579505590654385248