Nathan U. Blecharczyk ’05, co-founder and CTO of the $1.3 billion internet startup Airbnb, responded this week to public criticisms from his freshman roommate aimed at himself and Silicon Valley.

Blecharczyk wrote to The Crimson about a blog post in which web entrepreneur Aaron J. Greenspan ’05 criticized what Greenspan described as unethical practices in Silicon Valley that he said were perpetuated by Harvard graduates.

Greenspan also criticized his former Harvard roommate for being involved in email spamming in college. At one point, Blecharczyk was listed as one of the world’s most active email spammers according to an online tracker.

Blecharczyk co-founded Airbnb in 2008, and it has rapidly grown since its inception. The internet startup allows people to rent a bedroom, apartment, or other short-term accommodation from a private party rather than from a commercial hotel.

As Greenspan noted in the post, Blecharczyk’s company has stirred controversy recently for sending spam emails to people advertising vacation rentals on Craigslist.

Company representatives said the emails were sent by an outside company contracted by Airbnb.

Blecharczyk said Silicon Valley companies can run into difficulties in the development phase, but that individual incidents should not characterize the company as a whole.

“Building a business has some similarities to developing a relationship. With both, it is normal to have some bumps, even with the best of individuals,” he said.

“It would be wrong to make these bumps representative of the whole or to say that they happen due to malicious intent versus being a normal part of the development process,” said Blecharczyk.

Blecharczyk also defended Silicon Valley against Greenspan’s criticisms, “vehemently” disagreeing that the technology hub is, as Greenspan described, fraudulent.

“There is nowhere else on this planet with such a high density of individuals who are trying to change the world for the better,” he said.

Blecharczyk also said he thought it was inappropriate for Greenspan to reference Blecharczyk’s past when discussing his current business.

“I don’t think commenting on something that happened over a decade ago is either productive or helpful in this situation,” he said.

But he said he was not put off by his former roommate’s criticism.

“When doing something novel and disruptive, you’ve got to take criticism in stride,” he said.

“It would be a shame if his personal perspective were to cloud others’ perception of Silicon Valley or Harvard,” he said.

In a statement to The Crimson, Greenspan explained his reasons for speaking about Blecharczyk now, ten years after they lived together.

“The point wasn’t just to prove that Nathan did something wrong ten years ago. The point was that ... if no one ever talks about the fraud that everyone in Silicon Valley is constantly knee-deep in (and often has connections to Harvard), nothing will ever change.”

But Blecharczyk also rejected Greenspan’s criticism of Harvard, praising the entrepreneurial spirit on campus.

“I will say that I am impressed with the number of Harvard alums who have started tech companies over the past several years,” he said.