[yellowbkpk]

All addresses are pretty hard for computers to understand, so the people building the software to make them understand (geocoders) usually make them work for the most 'in-demand' address formats. Just like every other bit of software, finding the special cases and figuring out how to understand them is tricky.

http://www.columbia.edu/~fdc/postal/ is a pretty good overview of most of the postal addressing systems around the world.