So, this got me thinking.
First of all, Unabomber is exactly right. The reason so many parts guys INSIST on the VIN is that Murphy's Law will almost GUARANTEE that if they do not get the VIN, the customer is going to come back saying, "Weird, this part doesn't fit my car." Rework for the parts guy, no additional revenue, time lost. Sure, WE know what we're talking about, but average Joe may not, and lots of general repair shops don't know the difference between an '02 and an '04 WRX.
When I have to supply a VIN, I just look at my handy-dandy table of VIN numbers that I've gathered over the years, mostly from cars that my own shop-mates have owned. I have most of the common models covered.
Which brings me to: Could we have a thread that just compiled VINs of each year/body style/tranny type? We'd just need some volunteers like Unabomber to pitch in. I'll happily donate my Legacy GT VIN's... I'm sure in short order we'd have a very complete list, and nobody'd ever have to go asking again.