The SEC alleges in a civil action that Mr. Cuban sold his entire 6% ownership stake on June 28, 2004, after learning that Mamma.com was raising money through a private investment in a public entity, or PIPE. The next day, on June 29, the company announced the PIPE financing and shares of the company dropped by more than 10%. By selling his stake, the SEC alleges, Mr. Cuban avoided more than $750,000 in losses.

In a PIPE transaction new shares are issued at a discount to the current trading price. An announcement of a PIPE transaction is often followed by a drop in the stock price as shareholders anticipate their stake will be diluted.

(Illustration by the Wall Street Journal)