I think it would all depend on what they were willing to claim to be able to find learn or predict from your palm or fingerprints. Given some reported correlations like the ones between earlobes and heart problems, they might be able to come up with some generalities. For example, they could probably tell from the size of my hands I am male. Would it be a shock if they said I was at an increased risk for prostate cancer, but probably won't die while giving birth to a child?
What if all they provide are Barnum statements that apply to everyone? "You are happy at times, but also have bad days."
Then again if they can accurately and repeatedly tell me I will win the lottery in the future, and using which numbers, they might be on to something.