Lucas Arts is beginning to have trouble on their support forums.

Post as much as you can despite the mods attempts to ban Sam n Max 2 threads.

Make your voice heard.

Check out this particular post that has not been banned just yet.
It's a morphed version of Lucas Arts' press release to express your disgust.

http://forums.lucasarts.com/thread.jspa?threadID=133&tstart=0)

This isn't going to do anything but make LucasArts pissed off at you.

A far more effective way to get their attention is to mail pr@lucasarts.com . Someone is reading the email sent to that address (unlike the forum posts, which all get deleted), and also unlike the forum posts or petitions, if you mail pr@lucasarts.com you can add your voice to the thousands of others who have written in to express their feelings about the game being cancelled.

The point of this whole thing isn't to go and harass LucasArts to the point that they stop listening, its to let them know you think they screwed up.