Getting things delivered to the Republic of Ireland is a major pain because of this. I've had deliveries delayed because the company in question doesn't believe my address is real or correct. It doesn't contain numbers, the word 'street' or a postcode. Some sites also flag your order if you put 0000 in as a postcode for example. Some enterprising guys have created an unofficial "Location Code"[1] for Ireland to help solve some of these problems but it all comes back to faulty assumptions.
[1] http://www.myloc8ion.com/