The battle between Silicon Valley's two biggest boosters has flared up again, The Atlantic Wire has learned. It's an industry that takes its conferences very seriously: the conferences are where much of the business of launching, financing and selling new companies take place. In the last year, TechCrunch founder Michael Arrington and web entrepreneur Jason Calacanis, once partners in the influential and now defunct TechCrunch 50 conference, have been vying to stage the new premier venue for startups to pitch venture capitalists and launch new products to the trade press. With Calacanis's new conference Launch set to start tomorrow, sources say that Arrington is going all out--including using the weight of his powerful industry news blog TechCrunch--to squash his rival. 


Two sources tell us that Arrington has tried to persuade attendees and sponsors not to participate by threatening bad or--maybe even worse in the buzz-driven industry--no coverage on TechCrunch. One entrepreneur, who would only speak anonymously because he said he feared retribution from Arrington, said Arrington had told him his company would no longer be covered on TechCrunch if he attended Calacanis's conference. "Michael has told me that if I go to this, they'll never do business with me again," said the entrepreneur.

Calacanis refused to comment on whether he had heard reports of Arrington and TechCrunch trying to persuade attendees and sponsors to skip Launch, but he did say that no writer from TechCrunch had applied for credentials. "I think it's unfair to those startups and I don't understand how any publication could blacklist companies over a business dispute," Calacanis said. "I feel terrible about it." Neither Arrington nor AOL returned requests for comment. We'll update if they do.

This is not the first time that Calacanis and Arrington have clashed over the conference business. Last November, after Arrington had started his own conference series called Disrupt, Calacanis sued. He contended that when AOL purchased TechCrunch for a reported $25-$40 million, he should have received a portion of the proceeds. On the same day he announced the suit, he unveiled new details about his very own start-up conference, dubbed Launch.

This bad blood between between Calacanis and Arrington has played out relentlessly across comment boards and Twitter. And though many of their disputes come off as inane and petty, the conference franchise they spawned is anything but. Starting in 2007--shortly after Calacanis sold his Weblogs, Inc. to AOL--the conference has connected a number of pioneering start-ups with big name venture capitalists. Before dissolving in 2010, it launched Red Beacon, Yammer and Mint.com, which was later acquired by Intuit for $170 million. Also worth remembering: these are big ticket events, with general admission fares as high as $2,995.

The sources say that Arrington has urged sponsors--largely established tech firms and venture capitalists--to pull their names from Launch. Over the weekend, one noticeable logo disappeared from the Launch home page: Google.