Palo Alto’s Topix.net — a news aggregator purchased last year by Knight Ridder, Gannett and Tribune — will launch a free classifieds service intended to compete against Craigslist, according to E&P and Editor’s Weblog. However, by giving classifieds away, its classifieds will also compete against the paid classified sites of the newspaper companies that own Topics.net. “This is a big move for Topix.net,” wrote Edelman PR guru Steve Rubel in his blog Micro Persuasion. “It puts them squarely up against Craigslist – the giant that is eating away much of the newspaper biz’ revenue base. At the same time, it curiously provides a free alternative to existing paid services these companies run independent of their Topix JV [joint venture].” Topix won’t be limited to posting ads in its classified sections; it will be able to put, for instance, apartment listings for a particular city next to stories about that city. (Knight Ridder is expected to sell its share of Topix.net to McClatchy when the sale of its newspapers closes next month.)