About 80 percent of all people claiming to help inventors build a business, market their product, or raise capital are con men, beggars, thieves, or incompetents, cautions Professor Mark A. Spikell, co-founder of the Entrepreneurship Center at the School of Business Administration of George Mason University.

Alan A. Tratner, founder of the nonprofit Inventor’s Workshop International Educational Foundation (IWIEF), describes most invention marketing companies as cancers on the inventing community and a disease that needs to be eradicated immediately. Too often inventors lose large amounts of money and are derailed by the unfulfilled promises and come-ons of these companies, he says.

Dave Thomas created an improved joystick for video games. His wife, Susan, saw an ad in USA Today: “Have an invention? Need help?” They responded to the ad, and the company, located in Boston, was excited about promoting the device. There was just one hitch: it would take $10,000 to get it off the ground.

Then Susan’s brother-in-law, who believed in the invention, was killed in an auto accident. His widow provided the needed $10,000 from the insurance settlement.

Dave and Susan flew to Boston. The account representative wined and dined them. They signed a contract and handed over a $10,000 cashier’s check. And then? The account representative disappeared. The Massachusetts Attorney General’s Office didn’t have any record of the company.

Dave and Susan are now $10,000 wiser.