Another possibility (location based identifier): Reserve the first 2 characters as location indicators: AZ, PA, TX (states) and CH, IL, DU, RU (countries, etc.) This does however unfairly limit the number of caches within a state or country. As we all know, AZ would probably need more numbers than RI. ;)
I don't think that will work very well. You have correctly pointed out that large states may use up their allotment of numbers relatively soon, while small states may never use up their allotment of numbers. For example, Colorado used to assign license plate numbers based on the county that the vehicle was registered in, but abandoned that policy because urban counties have populations over 100,000 and thus were using up their allotted numbers, whereas some rural counties have under 1,000 people and thus used only a small percentage of their alloted characters.
Also, some countries codes you listed are the same as states - IL is also the abbreviation for Illinois, for example.
Ken (a.k.a. Highpointer)
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