Craigslist may be the world’s largest listings Web site, but after knocking down developers who try to build services on top of the Web site, it may also one of the least liked.

On Monday, 3Taps, a company that collects public data and organizes it for developers to use, filed an antitrust claim against Craigslist, accusing the company of anticompetitive business practices.

The lawsuit, which was filed in Federal District Court for Northern California in San Francisco, is a response to Craigslist’s lawsuit in July that accused 3Taps and Padmapper, a listings Web site, of infringing on Craigslist’s copyright and trademark.

Last month, in a Disruptions column, I noted that Craigslist had killed access to dozens of small Web sites and services that had tried to build products on top of the company’s listings. The developers and companies were sent stern cease-and-desist letters by Craigslist’s law firm, Perkins Coie.

Craigslist and its chief executive, Jim Buckmaster, did not respond to a request for comment.

In 3Tap’s lawsuit, which also answered questions posed by Craigslist in its suit, 3Taps said that although accomplishments by Craigslist were commendable, its dominance over classified listing was stifling innovation and hurting consumers.

“As Craigslist spends heavily to bully and intimidate companies that challenge them, consumers are deprived of better ways to find and execute real-time exchange transactions,” said Greg Kidd, the founder and chief executive of 3Taps, in a news release issued with the filing. “Craigslist uses its monopoly position to achieve huge annual profits without sinking any meaningful costs into research and development or innovation,” he said.

3Taps is one of the few companies to stand up to Craigslist. Many developers have criticized Craigslist for bullying smaller developers that do not have the resources to defend themselves.

“The basis of our antitrust counterclaim and defense against Craigslist’s baseless lawsuit is simple: public facts are public property – openly and equally available to all businesses and consumers.” Mr. Kidd said in the release. “Sham copyright claims and unenforceable terms of use cannot stand when they deceive users, intimidate innovators, or thwart a competitive marketplace.”



