Mark Cuban, the eccentric Dallas Mavericks owner and self-made Internet billionaire, was charged today with insider trading by the Securities and Exchange Commission.

Cuban, 50, is accused of illegally selling 600,000 shares of stock in Mamma.com, a company he himself had described as an "up and coming search engine" in a blog posting from 2005.

Problem is Mamma.com, a Montreal-based start-up now known as Copernic, began raising capital in June 2004 through a process known as a PIPE ("private investment in public equity") offering. Cuban knew of the offering beforehand and sold his shares hours before it became official, prosecutors allege.

By selling his 6.3 percent stake in the company, Cuban avoided more than $750,000 in losses, prosecutors say in court filings.

In a statement, Cuban denied wrongdoing and said he was "disappointed that the Commission chose to bring this case based upon its Enforcement staff's win-at-any-cost ambitions. The staff's process was result-oriented, facts be damned. The government's claims are false and they will be proven to be so."

Mark Cuban's attorney, Christopher Clark, defended his client on Fox Business Network, arguing that Cuban knew "there was going to be an offering...but that, that doesn't equate to inside trading:"

According to court documents, on June 28, 2004, then-Mamma.com CEO Guy Faure sent Cuban a message, titled "Call me pls." In the e-mail, CEO told Cuban to call him "ASAP." Cuban phoned Faure minutes later from the American Airlines Center in Dallas and spoke to Faure for 8-1/2 minutes.

In the conversation they allegedly discussed confidential information about the PIPE offering. At the end of the conversation, Cuban told Faure: "Well, now I'm screwed. I can't sell."

(Faure then wrote to other Mamma.com board members that "as anticipated (Cuban) initially 'flew off the handle.'")

After calling a sales representative to ask about the offering's details, Cuban called his Dallas broker and told him to sell his entire stake in the company, saying: "Sell what you can tonight and just get me out the next day."

On his blog, Cuban later wrote that PIPE financing was a "huge red flag" for him. "I don't want to own stock in companies that use this method of financing.

"Why? Because I don't like the idea of selling in a private placement, stock for less than the market price, and then to make matters worse, pushing the price lower with the issuance of warrants. So I sold the stock."

On June 30, Mamma.com's stock opened at $11.89, down 9.3 percent, and continued to decline over the next week.

The Dallas Morning News notes in an editorial today that it may be "hard to believe that a man as smart and as rich as Mr. Cuban, the Dallas Mavericks' owner, would risk jail to save $750,000 in dumping his 6 percent ownership in the Internet search company, Mamma.com, as the government alleges he did."

Wired opined that "regardless of how the SEC's insider trading case against Mark Cuban plays out, one thing is fairly certain: It won't be settled quietly." In the same article, Alexander Bono, the chairman of securities litigation in the Philadelphia office of Schnader Harrison Segal & Lewis, said that historically the SEC likes to make examples of "well-known individuals" like Martha Stewart, the television personality who was convicted in 2003 of illegally trading ImClone stock and served five months in a federal prison.

Still, as The Wall Street Journal's "Deal Journal" blog says, "insider trading is considered notoriously hard to prove."

Read the full court filings against Cuban:
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