Zillow’s recently-launched “Coming Soon” feature has been controversial from the start, with some real estate professionals proclaiming that it is a method to bypass traditional listing agencies. In fact, the “Coming Soon” listings from Zillow are forbidden by MLS rules in the company’s hometown of Seattle.

Now, Zillow is facing additional scrutiny over the feature, which allows home sellers to gauge interest on their homes up to 30 days before they are placed on the market. A San Francisco-based company by the name of Top Agent Network has sued Zillow, alleging that the company stole trade secrets in order to create the new “Coming Soon” product.

The lawsuit alleges that Zillow feigned interest in investing in Top Agent Network, simply to obtain details on how its system worked.

“TAN is based on the principle that collaboration among trusted participants is the key to success and we approached this transaction in that spirit,” said TAN CEO David Faudman in a press release. “We believe that Zillow broke this trust by misusing trade secrets that we spent years developing and perfecting.” TAN’s suit labels Zillow’s “Coming Soon” feature as an “imitation product.”

We’ve reached out to Zillow, and we’ll update this post as we hear more. Update: Zillow said it has not yet been served, and that the company does not comment on pending litigation.

The suit was filed today in U.S District Court for the Northern District of California. It notes:

Beginning in early 2014, under the guise of a potential investment by Zillow, Zillow was granted access to TAN’s confidential and proprietary information as well as its business strategy and model. Among other things, this included the proprietary system developed by TAN over many years related to the presentation and dissemination of pre-MLS listings. TAN provided this information under the assurance that Zillow would keep this information confidential, and that it would be used solely for evaluating a potential investment in TAN. After months of accessing TAN’s confidential information under the false pretense of a potential investment, in May 2014, Zillow admitted that it never had any intention of making an investment, informing TAN that this was “just not what we do nor have ever done.” Then, just four weeks later, Zillow rolled out—to great fanfare—a copycat product that incorporated confidential and proprietary information obtained from TAN.

TAN v. Zillow – Complaint – 10-27-14