The real Tsutomu Shimomura has a small cameo in the movie as an anonymous hacker. In the scene when Wong (Shimomura) holds the conference to announce that his software has been stolen, Logue (Lowe) heckles him about it. Sitting to Logue's right (to the left if you are viewing it), is the real Tsutomu Shimomura.
Editors of 2600 magazine (a hacker publication) learned of this film early in its development and were at the time campaigning for Kevin Mitnick's release from prison. They filmed the documentary "Freedom Downtime" as they tried to correct many glaring errors and personal attacks on Mitnick's character in the film, protesting outside Miramax offices in New York amongst other things.