[dsr_]

Let me make a suggestion: for reporting, return a URL with a set of word codes rather than numbers and letters.

https://aboutmybrowser.com/dog_walrus_banana_door

If you figure out a set of 1000 short words that are not too close to each other and easy to pronounce, four of them gives you a trillion possible combinations. If you window it so that the first word is always the same on a given day and keep a record of that list, you can differentiate a billion combinations in a day and have a good check that the information was gathered recently (or else is a thousand or more days old.) http://www.manythings.org/vocabulary/lists/l/ will get you common words, as a start.

[zethraeus]

This is especially brilliant in this situation because it would make the OP's website invaluable for over the phone debugging - the (unfortunate) situation in which it is most likely to be used. Numeral lists are anathema to phonecalls.

Great suggestion.

[muyuu]

That's a nice compilation. I used lists from here: http://www.bckelk.ukfsn.org/menu.html to programmatically compile a list for a similar purpose, and a markov-chain based sentence generator that I didn't use because it could generate sensitive stuff occasionally...

[sylvinus]

Beware that "walrus" may not be that easy to pronounce by a foreigner :)

[swalberg]

Using the 26 letters from the NATO alphabet might be easier, it's made to be intelligible for non-English speakers over a radio connection with static.

http://en.wikipedia.org/wiki/NATO_phonetic_alphabet

[mustardhamsters]

Good starting point, but that won't get him trillions of combinations.

[jerf]

It does with 9 letters. In this case though I think I'd use them like a counter, so I would probably still top out at around 4 or 5.

[hoov]

This reminds me a little bit of S/KEY: http://tools.ietf.org/html/rfc1760