Hazy memory, but three decades ago I read some research from the Open University in the UK that said, roughly, that the number of bugs found is a factor of the

Hazy memory, but three decades ago I read some research from the Open University in the UK that said, roughly, that the number of bugs found is a factor of the number of users. Some apparently "bug free" programs are actually riddled with bugs but they are not found because almost nobody uses them. They are probably not fixed for the same reason ;-)