In 2002, the Federal Trade Commission ordered search engines to make sure any paid listings in their results were properly labeled as ads. Today, after calls for the agency to update its aging guidelines, the FTC said it has sent letters to 20 search engines with requesting improved disclosures. Search engines are doing an increasingly bad job adhering to the spirit of the 2002 rules, the FTC said in the letter: "We have observed a decline in compliance with the letter’s guidance," the agency said.

The 2002 rules called for search engines to distinguish between paid and "natural" links. That advice still stands, the FTC said. But the agency has issued new guidance on how search engines should do that, emphasizing visual cues such as borders, shading, and text labels. That goes for newer forms of search as well, the agency said, including Siri-like voice search and recommendation-based products like Facebook Graph Search: "Regardless of the precise form search may take in the future, the long-standing principle of making advertising distinguishable from natural results will remain applicable."

It's still unclear how the guidelines will apply to specialty search engines where most of the results are the result of paid inclusion. Google Shopping, for example, includes only paid listings. As Search Engine Land notes, the updated FTC guidelines could mean that results pages on paid-inclusion search engines will need to be redesigned.