According to Ms. Hoang’s suit, the IMDbPro professional portion of the site, which charges an annual access fee, used her credit card information to learn her real name, Huong Hoang. Then, she asserts, the site “scoured” publicly available data to find and publish her birthday, July 16, 1971 — which remains posted.

Amazon’s lawyers and a company spokeswoman declined to comment, citing a company policy against public discussion of pending litigation. But in their multiple legal responses, they have alternately dismissed Ms. Hoang’s claim as “selfish, contrary to public interest and a frivolous abuse” of the court, and bluntly denied the assertion that credit card information had been used to identify her.

What the Amazon team has not done yet is to disclose how IMDb did, in fact, link the actress Junie Hoang, a stage name, with the IMDb Pro subscriber Huong Hoang, one of perhaps 600 people in the United States with the same name, according to a public records database maintained by Nexis. If credit card information had been used, Amazon’s lawyers say in court filings, there still would have been no violation of law or the company’s privacy agreement.

Indeed, data-mining of that sort could appear downright primitive compared with the online tracking and behavioral advertising addressed in a set of online privacy principles outlined for Web-based business like Amazon, Google, Yahoo, Facebook and others by the Obama administration this month.

But any court decision in the area will be closely watched.

“A judgment would likely be a great concern for the many companies who actively use mining services and information,” Jonathan Turley, a professor at the George Washington University Law School, said of Ms. Hoang’s suit in an e-mail last week. But he also pointed out that a dearth of specific legislation governing data use had left much in the hands of the courts.

Debate about age bias, Mr. Turley noted, has obscured the potential import of the case. “The age claim is so tenuous that it distracts from a legitimate concern over the mining of such information,” he said. Several publicists for movie stars, in fact, said last week that they had not collided with IMDb over age. “Age has never come up — just credits — and, yes, they were responsive,” said Kelly Bush, whose ID public relations firm has counted Ben Stiller, Dustin Hoffman and Diane Lane among its clients.

But IMDb looms large because of its reach — it claims more than 110 million monthly unique visitors worldwide and is often at or near the top of movie-related Google searches. And while its publication of vital statistics might not affect the stars, whose lives are widely scrutinized anyway, many second-tier performers and film workers believe the site exposes them to a film industry bias against older people.