The Wall Street Journal recently criticized the Adwords program because of a feature called session-based web ads, which, the newspaper writes, may cause some wev advertisers to overpay. WSJ says that the problem is that the ads are running within unrelated search results--meaning that the searchers within these topics are less likely to pay for the products and services advertised in the PPC ad. The article also points out that some advertisers have limited the scopes of their campaigns to prevent session-based clicks.
This negative publicity comes at a time when Google is struggling to reach small businesses and bring them into the PPC advertising program.