From a Legal Standpoint.

When you sign a Letter of Offer, it constitutes acceptance, with acceptance, it becomes a contract.

If you decide to bail on the company, does the company have a cause of action against you? answer is Yes.

BUT, generally most company's won't pursue a court action, perhaps because:-

(a) too petty;
(b) too costly; and
© they can't prove they suffer any loss or damage as a result of your departure (this case will be different if you are being paid and suddenly you decide to resign prematurely without giving notice); and

HOWEVER, one thing they can do is:

(a) blacklist you.

No one like getting stood-up and left in the rain without an umbrella, if you "think" it worth the risk by all means go ahead. It's your career choice/move.

My 2cents worth of advice, don't be fickle.