One victim thought that the thief was a prospective home buyer. Another believed that he wanted flyers for an upcoming theatrical performance.
The man stole wallets from each of them and is suspected in at least 14 other thefts in Thousand Oaks since February, Ventura County sheriff's officials said.
Sheriff's Sgt. Kitty Hoberg said the thief is described by some victims as a barefoot young man who goes door-to-door asking for help or information.
"Next thing they know, he's gone and the wallet is too," she said.
Most of the victims have been senior citizens who think that they are helping a stranger or homeowners giving a tour of a house for sale.
None of the thefts has been larger than $150, but the Ventura County Crime Stoppers is concerned about the increase in cases in recent months, said Hoberg, who heads the program. The group is offering its highest reward of $1,000 for information leading to the man's arrest.
The man is reportedly 25 to 30 years old and has used the name Steve Little. In one case, he was seen driving a white Toyota Tercel.
Cash appears to be the main item stolen, Sheriff's Detective Dennis Reed said. In most instances, the theft amounted to only a few dollars.
Credit cards were discarded along with the wallets, some of which were later found in parking lots and some in other victims' homes.
Nancy Roth, one of the victims, said the man who knocked on her door April 20 posed as a prospective home buyer.
Roth said she let the man in because he was polite. He called himself Steve and said he was from San Diego. Although he was only out of her sight for a few seconds, her wallet was missing when he left, she said.
Elinor Gustafson, 62, said she and her husband allowed a stranger to use a restroom at the Conejo Players theater May 4. Gustafson's husband was in the same room but didn't see the man take his wife's wallet. "It made me furious after I realized that we had been taken advantage of," she said.