The so-called sharing economy, dominated by the likes of Airbnb, Uber and Lyft, has attracted millions of consumers. So it shouldn't surprise anyone that scammers also have turned out in force to grab a piece of the action.

"We hear often about scam attempts," acknowledged Nick Shapiro, a spokesman for San Francisco-based Airbnb. "We tell people until we're blue in the face to never go off our site and never wire people money."

Home-sharing scams include bogus listings and aggressive efforts to get people to part with money before arriving for their stay. More sophisticated scammers might run the con by hijacking a legitimate listing.

The common denominators to each racket are that, at some point, the scammer will insist on communicating directly by phone or e-mail, or will steer people to another site to complete the booking process. Then a request will be made for money to be wired to a specific address.

The services basically serve as middlemen, ensuring that everything's on the up and up. The goal of scammers, therefore, is to get the sites out of the picture and deal one-on-one with potential victims.

You'd think no one would fall for this sort of thing, but you'd be wrong. For every 100 people who recognize a swindle taking shape, there will always be one who thinks he's getting a sweet deal.

That's the guy scammers are going after, the one who believes it when a purported Airbnb host says he can lower the price by cutting out the website and not paying the usual 3 percent commission.

A recent report by the Federal Trade Commission that estimated the total value of sharing-economy transactions at more than $100 billion shows the scope of the problem.

FTC Chairwoman Edith Ramirez said that "targeted regulatory measures may be needed" to protect consumers.

Still, it's a challenge to protect people once they're lured into one-on-one communication with a cheater.

Shapiro said Airbnb scans images in search of tipoffs that a scam may be in the works, such as a host including his personal e-mail address. When something suspicious is found, the listing is removed and users are notified.

"We immediately take action to shut them down," Shapiro said.

He said all communication between a renter and host should remain on the website until a deal is struck. Contact information should only be exchanged after a booking has been made. Airbnb only makes payments available to hosts 24 hours after a guest has checked in.

The site has a security section that runs down what you need to know to protect yourself. It's worth a read.

The company also notifies users multiple times during the booking process not to be duped into going off-site or circumventing Airbnb's payment system. Pay attention. These warnings are for your own good.

Shapiro advised travelers to always read a listing's reviews before booking a property, especially other guests' reviews of the host.

"As things like this become more popular, there will be more attempts at scamming," he said.

In other words, watch your back. Not everyone you'll meet in the sharing economy has your best interests at heart.

David Lazarus is a Los Angeles Times columnist.