Schrodinger's Bus: You do not know if you will be hit until you are already in the street. I feel like there is some promise in naming a band this, but it is unfortunate it so often is what people have to deal with when bringing an item to market.

... but you can still fail to notice one, and you can gauge and to some degree control your risk of being fined.

In fact, if you sell 10 hobby prototype boards to other hobbyists, you probably have a higher risk of getting hit by a bus on the way to the post office than you do of being fined.