My understanding of the SEC has evolved since I just finished the Snowball Warren Buffet book (http://www.amazon.com/Snowball-Warren-Buffett-Business-Life/...). There is a section that discusses his run in with the SEC and there is a behind the scenes discussion before charges are pressed (in WB's case, not pressed). I think Cuban has already had a chance to defend himself behind the scenes, and despite this the SEC is still deciding to prosecute. This has example written all over it.
Aside from the timing of the trade and the fact that the calls took place, everything in that report is based on the word of the CEO of Mamma.com. I honestly don't know if that matters, I'm not a lawyer and I don't play one on tv. But if it does matter, if the line between legal and illegal is whether the other party told you that you were receiving private information, then it's pretty shitty that you could be found guilty based only on that other party's say-so, don't you think?
Read the statement of facts in the PDF as well: (http://sec.gov/litigation/complaints/2008/comp20810.pdf). After reading it, chances seem slim that he's innocent.