Still, it's most annoying -- especially since today's lunch trip to a nearby Apple store ran into their Jobs memorial closure.
Naturally I'm inclined to believe this is a national disaster, but this isn't a trending topic anywhere. So it's probably just bad luck.
Researching this did lead me to a related topic of interest. It's safe to use a higher wattage adapter with the Air, specifically the current MacBook and MacBook Pro adapters ...
... Power adapters for Intel-based Apple portables are available in 45W, 60W, and 85W varieties. Although you should always use the proper wattage adapter for your Apple portable, you can use an adapter of a higher wattage without issue.
For instance If you have a MacBook (13-inch Late 2009) that normally uses a 60W adapter, you can also use an 85W adapter with that computer. You would not use a 45W adapter with that computer; it would not provide enough power for that MacBook...I've read elsewhere that using a lower power adapter might allow the machine to function, but not to charge.
The article, incidentally, tells us the removable AC plug on Apple's power supplies is a "Duckhead". Who knew?
Update: On the advice of Dan Swift (see comments), I tried a fix that I thought was 90% crazy. First I confirmed I didn't have a 'stuck pin' problem. I checked all connector pins were moving and out. Then I charged it for 30-45 minutes on a friend's 'good' charger. Then I tried my charger. Now it works again.
This is the weirdest thing I have seen in years. I assume there's no OS in the (bloody $80) charger, so I assume this is a MacBook PMU glitch that will need a firmware update to fix.
Thanks Dan. I've changed my post title to make this easier to find.
I've posted on this to Apple Discussions.
Update: It's back to not working, which feels saner to me. I did reset the SMC, which may help when "The MagSafe power adaptor LED doesn't appear to indicate the correct activity". So it's to the Apple Store sometime soon.
I did find an article on a similar problem from 2008 that tells me that firmware issues can alter charging behavior: "In certain situations when you connect a new 60W or 85W MagSafe power adapter to the MagSafe port of an older MacBook or MacBook Pro computer, the adapter may not charge the computer and the LED indicator light on the MagSafe connector of the adapter may not illuminate."