The hot vacation rental service Airbnb has been insisting its recent scandals have all been innocent mistakes: The time it spammed Craigslist, its dearth of safety protections, the cover-up it attempted. For penance, the company built safety systems like a "verification dashboard," online references, and address confirmation.

All of which, it turns out, are overseen by a guy who was once among the world's most notorious spammers, who used to get threatening letters from the feds, and whose college roommate is now speaking out about his scuzzy past.

Nathan Blecharczyk, a co-founder of Airbnb and the company's chief technology officer, was once listed on Spamhaus's "Register of Known Spam Operators," a roll of "hard core... spam gangs" and people who run "committed hard-line spam operations" There are typically only around 100 people on ROKSO; to gain admittance, you must get kicked off three internet service providers for spam offenses, and to stay on it you must get in trouble again within six months.

The spammer listing was brought to light by Aaron Greenspan, who as a Harvard freshman was a one of Blecharczyk's roommates. Greenspan, who runs a mobile payments company, is also known for having won a settlement from Facebook over its name. Yesterday Greenspan blogged about his experience with Blecharczyk:

What most people don't know is that during our freshman and sophomore years of college, Nathan was one of the top 100 spammers in the world... While we were roommates, Nathan ran a sort of enterprise called Data Miners out of Grays M-54 in Harvard Yard using a variety of aliases for himself. Data Miners would hop from service provider to service provider each week, sending millions of messages at a time. Nathan was clearly brilliant—he had designed both custom hardware and software to send these messages in bulk as efficiently as possible—and he paid his way through college thanks to these endeavors, but what he possessed in engineering skill he obviously lacked in morals. Though our desks were only a few feet away, I refused to have anything to do with his business...

By our junior year, I remember learning that Data Miners had been shut down. Nathan told me that he had received threatening letters from the FTC, which made sense, because he had often been using insecure government servers (meaning taxpayer dollars) to route his illicit payloads.

Blecharczyk may still be at it.

In May, a competitor showed how Airbnb shills were emailing people who had listed rental properties and spare bedrooms on Cragislist, trying to get them to move their business to Airbnb. These emails were sent out systematically, including to people who had specifically ticked a box indicating they did not want to receive commercial offers. They were sent from anonymous Gmail accounts to obscure Airbnb's involvement. It was at best a hugely sleazy way to drum up business, even by Silicon Valley standards. At worst it was illegal.

Airbnb has yet to officially comment on the scandal. But in the press, an anonymous executive tried to shift blame to rogue remote contractors. We didn't buy it, and neither does Greenspan:

Gawker's Ryan Tate asked, "Did Airbnb Scam Its Way To $1 Billion?", as did other major news publications. The answer is most likely yes... When I initially read about Airbnb's spam scandal, I could and could not believe it. I thought that Nathan had learned his lesson—even if he wasn't directly responsible for writing the code behind the messages, he clearly should have known better than to allow them. Apparently he did not.

We emailed Blecharczyk, his press team, and one of his investors yesterday afternoon and have yet to hear back. But we're not holding our breath.

Airbnb's investors, led by cone-headed Silicon Valley svengali Marc Andreessen and tawdry Russian arriviste Yuri Milner, pumped $100 million into the company after the Craigslist spam scandal and after it emerged Airbnb initially ignored a customer whose apartment was horribly ransacked, then tried to hush her up to protect the funding. Why should Airbnb try to prove it is not run by the worst sort of sleazeballs, when its sleazeball behavior has already been rewarded?

Airbnb is no doubt content to continue to pretend to be really, really sorry about how its customers have been pillaged, to highlight all the nifty electronic systems it has since buit to protect those customers, and to describe Blecharczyk as someone who "uses data to identify and pursue high-growth opportunities." That description of the programmer's activities is as 100 percent technically correct today as it was when Blecharczyk was in college. If you want to find out what exciting new ways the hard core spammer has dreamed up to convert your personal information into "high growth opportunities," you can sign up right here.

[Photo of Blecharczyk, top, via Airbnb]