This thread on Flyertalk has just been posted. Qatar has had a mistake fare published for quite some time that allows you to fly from Phnom Penh (Cambodia) to Doha in Qatar's Business Class to Saigon, Vietnam. In the process you earn about 20,000 Qatar miles for a Round trip (10,000 for the One-Way). This fare books in I which is the new booking class for Business on Qatar from on Oct.1. It usually earns 125% i.e. Avios. The US Airways partnership still seems to exist so you can also earn US Airways Dividend miles. American Airlines hasn't published any earning chart for Qatar yet.
Last year I flew Qatar A320 business class and was blown away by the product. It's a single-aisle plane but business class is actually better equipped and better food than on their A340s. I haven't tried the A330 setup though.
I'm in the area anyways and always wanted to make a 'stopover' in Doha – so this is very tempting!
You can find it on Qatar's website only not on ITA Matrix or Expedia. That's probably the reason it still exists.
There is a $40 cancellation fee should you book now and not have the time to actually make the trip.
Also it's possible Qatar does not honor the booking. Please DO NOT CALL the airline – wait a couple of days or weeks and just book online!