On July 26, an owner of a holiday home received an unusual message through the "contact the owner" feature of TripVillas, an Asian vacation rentals service -- where he had listed his property.
The message read:

Saw your property on here. Was wondering if you ever heard of Airbnb.
You can post your property on airbnb.com/newhost and enter code TWJJRM and youll [sic] get a $50 USD listing bonus.
Would be a great way to diversify the sites that you post your vacation property on.
Enjoy
The owner complained to TripVillas. It turns out he wasn't the only person targeted.
A single spammer attempted to send 302 messages through the service's system, according to Roshan D'Silva, the Singapore-based CEO of the site. After the first few went through, spam software held the rest for manual review.
The spammer ("John") used a generic e-mail address, not a company email address, and did not identify himself (or herself) as an employee or contractor of Airbnb.
Airbnb: Spammer or victim?
This was worrying. D'Silva wondered if Airbnb, an accommodation rental start-up based in San Francisco, was sending unsolicited messages touting its marketplace to the owners of vacation rentals.
The spammer was patient. To contact 302 users, he or she had to click on the "contact the host" link for each individual listing. All of the owners he attempted to contact were in Taiwan and Japan, a small slice of the 12,000 properties listed on TripVilla.
D'Silva first thought that maybe this was a rogue operator. Perhaps the promo code wasn't valid, and the message was a ploy to farm information from people.
But he used the promo code himself, and it worked: $50 was credited to his account as a new owner and would be received after a first booking was completed.
D'Silva interpreted this to mean that the promotion was legitimate and that Airbnb is "paying owners to list." He attempted to contact the company via its official Twitter and Facebook accounts, but didn't receive a response. He couldn't find an e-mail address on the company's website for fielding complaints.
Airbnb responds
Tnooz received this response from Airbnb by e-mail today:

This was a case of an Airbnb user abusing our "Refer a Friend" program (www.airbnb.com/referrals) to send out mass emails.
Our "Refer a Friend" program makes it easy for our users to share Airbnb with their friends or family (these sort of referral programs are fairly common among web companies).
We don't condone this sort of abuse of it, and we've shut down the referral code and the offending user's account. I've reached out to the folks at TripVillas to apologize for the inconvenience.
The company gave no indication of how widespread the abuse of this promotional code by the individual was. Tnooz contacted the spammer, too, but didn't receive a comment.
TripVilla's response
D'Silva says:

The "Refer a Friend" program does not give out a coupon code.
It allows Airbnb users to send out emails through the Airbnb platform and Facebook and does not allow them a code that they can use while messaging via other websites or put into their own email program.
I'm chalking down their response to being in a hurry to brush off something that is obviously not high priority for them.
I believe that such tactics are interesting to note and probably interesting to read about.
Tnooz confirms that a member doesn't receive a six-character code via the Refer a Friend program in any way we could find among current offers.
A broader problem?
A quick Internet search on the now-defunct promotion code TWJJRM found 30 links touting how you could go to airbnb.com/newhost, enter the code, and (if you're a member) receive $50 in credit.
Some websites, such as ireferyou.co.uk and RefAround, encourage existing members of Airbnb to solicit random strangers in the hopes that they can receive credit. It's a way to game Airbnb's legitimate program.
Between December 2012 and now, multiple people have posted the same promo code with the same encouragement to send out unsolicited messages to increase the chance of receiving promotional credit from Airbnb.
We found other codes online. For example, WN8FAE and DW3EPS, which both tested as valid on this reporter's Airbnb account when he entered them this morning.
It's unclear how many of these promo codes are floating out on the Internet, but it seems like at most a half-dozen currently. Airbnb's response to Tnooz's query didn't show any interest in this as a potential problem.
A Tnooz search for appearances of the spammer's e-mail address across the Internet showed the footprints of someone who has been interested in coupon codes and online marketing for quite some time, and who is associated with a New York City address.
Though there was nothing conclusive about what we found, it is quite possible that the rogue spammer was trying to take advantage of a get-quick-rich scheme that he or she found in an online forum.
Spam in the back cupboard
Since it was launched in 2008, Airbnb has enabled several million people to find places to stay. But it has also had its a couple of minor scandals. In 2011, Airbnb confirmed that its salespeople made unsolicited approaches to property owners on the classified listings service Craigslist.
The company admitted that was not a best practice, and put a series of checks in place, such as a requirement that new property listers must go through a "verification dashboard" and confirm key details, such as their address.
The company's chief technology officer, Nathan Blecharczyk, is familiar with accusations of spamming. After founding an online marketing company while in high school, he was listed as one of Spamhaus's "Register of Known Spam Operators," a rollcall of online marketers who have been blacklisted by at least three internet service providers (ISPs).
We all do crazy things when we're young and learning. And none of the behavior mentioned in this article was illegal, according to experts who have commented on similar cases elsewhere.
But there's no freude like schadenfreude, and it seems like Airbnb is becoming -- in a tiny way -- a victim of its own success, by attracting Sirens of Spam, like this lady: