JamesCherrill: there is nothing wrong with isSelected.
my point is (for instance)
you are filling in a form, and you get:
"Are you married: " <checkbox>
if validation returns false if the checkbox is not checked, no single person will ever be able to complete the form.
the problem with components like that is: if it's not filled in or checked, you can't really know whether it is a mistake, or it is providing the correct answer.