Here's a tip: If a Web site takes pains to assure you its offer is "risk-free," it almost certainly carries plenty of risk. In fact, just last year the FTC cracked down on an international scheme that offered "risk-free" trials of everything from weight-loss pills to penny auctions and charged the customers with exorbitant monthly charges.
"Although the defendants offered a money-back guarantee, consumers were often unsuccessful in canceling the charges or obtaining refunds, and the process involved time-consuming phone calls and other steps that made the deals far from risk-free," the FTC explained in a statement.
There are certainly legitimate businesses out there that use this phrase, but in general it's a case of "methinks the scammer doth protest too much." If a guy ran up to you and the first words out of his mouth were "Don't worry, I'm not going to stab you!" you would probably turn and run away. Do the same for "risk-free" offers.