>>When we tell our customers to use a UPS, they undersatnd that we are responsible and want to take care of our customers. Be aware that without a UPS you can never guarantee that your customers won't lose data. Make sure that your customers understand this!
>
>Of course, I agree with you.
>But this particular user makes backups regularly, and it has printed data so if anything goes wrong with table, user can easily restore database and insert missing data.

So you tell them "nothing is lost - this is the black Friday for which you were diligently saving these copies... now where's the latest backup?".