OpenTable Operations Associate interview questions

Interview went great and long story short I got a formal, written offer which I signed. The next day they rescinded the offer due to an issue with "references," even though the references I provided were never contacted. (I assume they went to some back door reference). I of course was shocked that a company would be so unprofessional to give a FORMAL job offer before dotting every i and crossing every t. If you're willing to rescind a job offer for whatever reason, you take care of that reason before giving an offer!!! Doing this can cause someone to resign from a job only to get their offer rescinded from you. Disgusting and unprofessional culture.