But it made me laugh

Not real. But, kinda funny the first hundred or so times you read it.

;( I'd not seen it before

Cute.

Knew it wasn't real when they did the joke about the wet floor sign in a carpeted area. Ever been inside a K-mart? No carpeted areas.

This letter is so fake. Although the addresses of the store and the person being threatened are in the US, the last line of the addresses is abnormal. The date isn't in "US" format (would have been written "March 12, 2005"). Layaway is a much more common US way of saying Lay-buy.

The real giveaway for me is the use of the term "lay-buy" instead of "layaway" in a letter sent within the US. "Lay-buy" seems to be an Australian English term.

Other things are the fact that it's digitally rendered instead of scanned, use of the spelling "offences" instead of "offenses", the date format, terrible grammar, spelling, capitalization, and punctuation, the use of a subdivision of a city in the address, and a comma before the ZIP code, None of those is a giveaway on its own (he could simply be a bad writer) but all added together, it seems very odd.

Where is that English/American thread?

Layby in English is a bit by the side of the road where you can park up to rest/eat sandwiches

I'm not sure what the equivalent of layaway is.

A quick Google shows that lay-buy is Australian. Do we need an English/Oz thread too?