Staying in the USA longer than 6 months

What are the penalties if a Canadien were to stay longer than 6 months in the USA? Is there any information actually out there regarding Canadiens who have crossed the border without a visa and stay longer than the mentioned 6 months?
I know we do not have to have a visa to visit the country for less than 6 months but if you pass that time what could happen?

Duplicate thread: http://www.canuckabroad.com/forums/cana ... t4629.html