Refusing an offer after accepting it

#1

What happens if I refuse an offer from one of the Big 4 after previously accepting it?
To be more exact, I have accepted an offer from one of the Big 4 a few months ago but have since started applying to other (potentially more interesting) jobs. Are there any legal consequences if I decide not to take up the accepted offer?

#2

Not really. Im sure they wont mind as they havent actually paid for anything.

#3

people do it often

they will just give someone else the place