I find a lot of these t-shirt messages hilarious and I love T-shirt hell - there are some highly inapporopriate, but hilarious messages. But, I agree with starl that there are children around, and because of that, I wonder if anyone actually wears these t-shirts in the street.
I would never dream of wearing a t-shirt where children might see me, that had a joke containing a swear word or inappropriate reference, no matter how funny it was.