My credit card is the only item I'd worry about. Well, also my phone if it's in the bag. I carry only crossbody bags, as I like the way they free my arms, so I don't worry about purse snatchers. It would be pretty hard for anyone to get the bag without ripping my arm off.
But I've been reading about purses being snatched in restaurants when women hang them on the backs of chairs. I will not hang my purse that way again, after reading that. They can grab the purse and be out the door before you even realize the purse is missing! Just keep it on your lap.