In September, Italian police seized the equivalent of 220,000 bottles of cheap wine that was accompanied by false documentation that claimed it was premium wine from Montalcino, home of the renowned Brunello wines. Police estimated the cache would have had a retail value of about 5 million euros, or $6.5 million at the time of the bust. A month earlier, a New York judge sentenced Rudy Kurniawan, a Southern California wine collector and seller, to 10 years in prison and ordered him to pay $28.4 million in restitution and forfeit $20 million in property. According to the court, he had for years carried out an elaborate fraud in which he blended lesser wines to mimic rare vintages, put them in old bottles, pasted false labels on them, and sold them to wealthy buyers.

Even Fred Franzia, chief executive of Bronco Wine, the company that makes what is known as Two-Buck Chuck, was once caught mislabeling grapes. After he pleaded guilty to conspiracy to commit fraud in 1994, he and his company paid $3 million in fines.

The Jeff Hill case has reminded the California wine industry of the risks of deception, said Ned Hill, the Sonoma vineyard manager. “Everybody is a lot more careful now about asking questions,” he said. “It’s made people dot their Is and cross their Ts.”

Given the scale of Mr. Hill’s purported fraud, those hurt by his actions are wondering why federal authorities have not brought any charges against him or the winery. Bryan Tong, the Napa County prosecutor handling the Del Dotto theft charges, said he had had no contact with federal authorities. Still, liquor regulators are keeping a close eye on the wines touched by Mr. Hill.

When Mr. Westfall of Invino, the online wine retailer, bought thousands of bottles of Hill Wine’s pinot noirs and cabernet sauvignons for $5 each at a bankruptcy auction in September, one of the T.T.B. agents on the case quickly contacted him, he said.

She told him that three of the cabernet bottlings, claiming to contain grapes from the Stags Leap, Coombsville and Atlas Peak areas of Napa County, were mislabeled and could not legally be sold in the United States without changes. Mr. Westfall said he sold about 1,800 of the questionable bottles overseas, but is still searching for buyers for 7,200 bottles.

The T.T.B. raised no objections about the rest of the wines that he had won, including the high-end 2011 Jeff Hill cabernet that my wife and I enjoyed so much that day we visited the winery.