Gallery Contracts - what are your thoughts?

I was recently working with a group that is putting together a group show.  There was no contract with the hosting gallery.  Now the gallery is backing out of publicity.  There is no contract so no way to hold them to what was prior understood as part of the agreement.  What are your thoughts?  Would you do business with a gallery without a contract?  Do you consider it unprofessional?  What standards do you hold yourself and a space to when showing your artwork?  Thanks in advance for your feedback.