[nibs]

I would never hire someone back who accepted and then bailed on a job offer. I would hire someone back who rejected a job offer and got back in touch at a later time saying circumstances have changed. I think once you make a commitment to someone that you will do something, and then you do not do it, regardless of the legal repercussions most people will not want to hire you as a result.

It is possible that you are amazing at what you do and that they will bend over backwards to make a spot for you even if you abuse them. I suspect however the good advice for 90% of people asking that question is only take the start-up job if you never want to work for Facebook or the person who offered you the Facebook job.