Can Companies Rescind A Job Offer?

Alfonso Espitia asks: "Just had a question for the general audience out there. I recently got recruited by a company, went to their job fair and the whole nine yards. After the fair I was sent a job offer, I then accepted filled out all the paper work and sent it back. I was given a start date and everything. About a week and a half or two I got a message on my answering machine saying 'About the offer that was extended to you...it is now rescinded.' Can they do this? All the paper work was filled out. I think I was more in shock that they would leave a message like this a few days before Christmas. Instead of just saying "It's urgent that we get in contact with you, can you call back?" Has anyone else had an experience like this? It's a -really- big company, so I didn't mention their name. Also, what can I do about this? Anything? I haven't tried to contact them yet, my recruiter is on vacation 'til the 2nd." I always thought an offer letter was a clear intent to hire, and that companies can't do this without penalties. Has this happened to anyone else? Is there anything Alfonso can do in this situation?