I looked this up a while back out of curiosity. Based on what I read, if you just stop coming in, the company is entitled to come after you for damages although, in practice, this probably doesn't happen.
For example, in New Zealand many employment contracts have an abandonment clause that basically says if you don't show up for 3 days, the contract is terminated and you've forfeited any accrued leave or other benefits they might have owed you otherwise.