There's another thread under Mileage Run you might want to take a look at that basically asks the same question. It's called "How many such error fare have you guys seen?" and is currently on the second page. It contains a pretty good rundown of the errors over the last year or so. There have also been some pretty nice deals that weren't errors. $199 on Jan. 1, 2000 from SFO-NRT r/t on CO(NW) was a good deal that wasn't an error.