A search on MySpace.com brought up more than 700 recent comments that accuse others of stealing headlines, user names, songs, background designs and entire profiles. In a recent survey of more than 400 online daters commissioned by Engage.com, 9% of respondents said they copied from another person's profile; 15% suspect their own words were stolen.

A Match.com profile of a man in Redmond, Wash., includes this postscript: "Shame on the woman who plagiarized my narrative and stole it for her profile!" And a 34-year-old woman in Basking Ridge, N.J., tacked this P.S. to her Plentyoffish.com profile: "To the girl who copied my profile -- and denies it...you s-!"

The quest for originality has spawned the services of online-dating coaches and profile writers. Some of them are victims, too. Dave Mizrachi, 34, of Miami sells an "Insider Internet Dating" course for $97. Mr. Mizrachi includes his own dating profile, advising men to use it as a guide. But at least 25 people on Match.com have stolen his lines, including: "I get a lot of women emailing me, (which is great for an ego boost)." One man uses Mr. Mizrachi's photo.

A recent search on Match.com brought up more than 90 profiles with such lines as: "I want an opposite. A yin to my yang," or "You know that woman who is the first person on the dance floor at every party? That's me." They weren't even from real people. They were cribbed from sample profiles posted online at E-Cyrano.com by dating coach and profile writer Evan Marc Katz. "It just seems so short-sighted," says Mr. Katz, of Los Angeles. "Everybody steals the same lines so they are not original anymore."

Thierry Khalfa says he had a good excuse to copy: His English isn't so good. The 44-year-old Frenchman first cobbled a ho-hum profile that said he liked to cook and enjoyed walks on the beach. Then he stumbled across the profile of Mike Matteo, 47, a screenwriter in Tampa, Fla. Mr. Matteo's profile had such nuggets as, "I have a sweet tooth, love my strawberry twizzlers and cheesecake jelly beans."

Without thinking twice, Mr. Khalfa says, he copied Mr. Matteo's prose because it also fit him to a tee. "That guy should be proud," says Mr. Khalfa, of Largo, Fla., who runs an auto-glass business. "In France, in the fashion business, when you see something that looks good, you take it and you copy it."

Mr. Khalfa caught the eye of preschool teacher Marjorie Coon, 48. They exchanged emails, and Ms. Coon wanted to meet Mr. Khalfa in person. Then she discovered he had copied the profile of Mr. Matteo, by coincidence her friend. She let Mr. Khalfa know she knew and dumped him. "I felt he was less than honest, a manipulator and downright stupid," says Ms. Coon, of Largo, Fla. Mr. Matteo wasn't too happy, either. "I'm not Cyrano de Bergerac," he says, referring to the 19th-century play about a man penning love letters for a rival.