With millions of Americans frustrated and bewildered by the trouble-prone federal website for health insurance, con men and unscrupulous marketers are seizing their chance. State and federal authorities report a rising number of consumer complaints, ranging from deceptive sales practices to identity theft, linked to the Affordable Care Act.

Madeleine Mirzayans was fooled when a man posing as a government official knocked on her door. Barbara Miller and Maevis Ethan were pitched by telemarketers who claimed to work for Medicaid. And Buford Price was almost caught by another trap: websites that look official but are actually bait set by fly-by-night insurance operators.

Some level of fraud or abuse is predictable with any big government program, and administration officials expected a few bad actors to emerge. Attorney General Eric H. Holder Jr.; Kathleen Sebelius, the secretary of health and human services; Edith Ramirez, the chairwoman of the Federal Trade Commission; and other officials met at the White House in September to discuss possible pitfalls.

But now, the technical failures troubling the website, as well as the law’s complexity, threaten to make matters worse. Only a tiny fraction of Americans have been affected so far, but state authorities and the F.T.C. are reviewing the issue aggressively.

Add dispersed attacks by con men (both real-world and electronic) to a single point of failure ( and you have a recipe for failure on a truly federal scale.