I like this last comment and thought it was somewhat true - the others are not worth a response. Yes, I'm sure if you sign into a contract where your employer is relying on you because they must honour their contract with clients too and then decided that you want to back out, it will tarnish your relationship with that employer. That seems to be common sense and from my experience in the business world, in Canada, fighting with your employer will make your life difficult. Just focus on keeping relations strong by sticking to your word, working hard and your employer will often reciprocate this attitude. The content of internet posts tells a lot about a persons character because they feel they can vent their anger without any personal consequence (cowardly act and very different to real life).

Do not bother coming to China if you are not mature enough to honour your contract. If a year is too much, sign up for a four month, one term contract and avoid those pesky school holidays. I want to repeat that these companies are businesses not travel agencies funding your adventure to China. If your someone who is committed to fulfilling your obligations and work hard when you need to, teaching ESL in China is a great opportunity. If your someone just looking for something to do because you cannot find a job straight out of university, you should consider backpacking instead (from my experience - SE Asia and Europe are both very nice).