I should imagine that people just ignore any letters in the hope that the problem will go away. And tell anyone who comes to the door that they never received it.
It happens all the time Witzend; which is why debt collection post is frequently sent by Recorded Delivery and has to be signed for. But then some refuse to sign for it because they know what it contains, which is why hand delivered letters are done and photographing it taking place.
Vampire is absolutely 100% right when she says that acknowledgement of the debt and working with your creditors to come to an amicable agreement that you can afford, is the very best way forward. No matter how small an amount you can afford, it will be accepted; but keep to the agreement and liaise with your creditors regularly if you have problems. Brushing debt under the carpet and pretending it doesn't exist is the very worst thing to do and only exacerbates the problem.
Tales about "stingy" guests and hosts.