I recently worked for a company that hired a mid-career manager after an extensive interview process. They waited 4 weeks for her to start and on the day she was supposed to start she texted her supposed boss to say she changed her mind. They were ticked. And within a week no one thought anything about it. So this manager did, in fact, ruin any chances of ever working for this company but it was the unprofessional way in which she handled the communication that put her on the no-hire list. If she had given them some notice and called or emailed to discuss the matter it really would have not been that big of a deal. Companies hire (and lose employees) on a regular basis. That doesn’t mean you should accept a job without meaning to take it and it is unprofessional to take a job and keep job hunting but if your circumstances change after you accept a job (and yes, that includes getting a better offer from previous interviews) then no one in corporate American would blame you for rescinding a job acceptance as long as you behave responsibly, politely and professionally when you do.