[hdjrudni]

Not sure about that. Some folks would argue you should always use surrogate keys.

I probably wouldn't for country_code specifically, but for most things its useful even when you have a 'natural' key.

[rixed]

It can be useful in some cases but can also be a hindrance. First because identifiers are more useful when they allow to actualy identify the thing; and also because now they can change from instance to instance, from customer to customer etc...