MacOS – MacBook Pro Serial Number Not Available

Apparently the only ways to find out a Mac's serial number (if you don't have the Mac physically present) are:

When you had the Mac, you:

• Registered it with Apple (check your support profile at apple.com)
• Ran and saved a copy of System Profiler's output

Without the Mac:

• Have a sales receipt from a retailer that puts the serial number on their receipts
• Purchased it from a retailer that keeps track of serial numbers
• Find the box the Mac came in

Thankfully, after I posted this question, the buyer was able to find the original box, which gave him the serial number.

But the actual answer to the question is: No, Macs do not normally store their serial number in a disk file.

In general, extended warranty plans are a healthy-sized profit center for the company offering them. This implies that unless a product turns out to be less reliable than predicted, on average (mean average) customers will be better off paying for their own repairs without the warranty. However, if one can't afford to self-insure for abnormal or even normal deviations from the average, something like AppleCare will lessen the downside financial risks.

Thus, I suggest (and buy) AppleCare only if an Apple product seems to be getting numbers of reports of below average reliability (e.g. the Duo 2xx and PowerBook 5x00 product lines). For other Apple products, maybe put the money in a savings account instead, and there is a good likelyhood that you'll end up ahead after a decade or two of Apple products.