I, for one, hate the two-letter postal abbreviations and I never use them.

Anyway, they seem entirely inappropriate for an international medium like the Web. I have seen numerous discussions get derailed when Americans confuse non-American participants with postal abbreviations.

Furthermore, the postal abbreviations for states are entirely superfluous in terms of delivering the mail. Postal codes are already mandatory, and they are much more granular than state abbreviations.

A third thing that bothers me is the way that people misuse commas when using state abbreviations (although this also does happen when not abbreviating). As in –

I went to Ithaca, NY for the summer.

You can't use a single comma like that! This kind of usage tells you that you can break the sentence at the comma and that two principal elements of the sentence are "I went to Ithaca" and "New York for the summer." That makes no sense.

It should be –

I went to Ithaca, NY, for the summer.

That tells you that the "New York" part is an appositive or parenthetical and can be safely removed without harming the meaning of the sentence.

Look up the list of "old" state abbreviations, and you will find no consistent form. You may also find that you don't remember the old forms any more. Since the USPS has a standardized format, we might as well learn and use it. Admittedly, having lived in AL, AR, and AK, but not AZ, the ambiguity among them could become confusing.

On a sort of related topic…what about the 2-character ISO country codes?

In my work, I deal almost exclusively with countries outside the United States. When communicating with coworkers in email, I pretty much always use the ISO country codes instead of writing out the country names. As much as I need to refer to countries, I'd really rather type "PK, IN and TH" instead of "Pakistan, India and Thailand."

But that's only with colleagues who are involved in the projects and know what the country codes mean. The program we use uses the country codes so it's a common denominator. I would never use them in documentation for users or with non-project colleagues.

For the most part, you can kind of figure what the codes mean…except for Switzerland which is CH. Or Croatia which is HR. Or Algeria which is DZ. Ok, so maybe they aren't so figurable…