These times of algorithmic flight loading and canceling/combining 'underbooked' flights really stink.
I once ended up flying a Seattle - Boston redeye on a 747 with a total three other passengers, and the flight crew said that they (Braniff Air, bought by Northwest, etc.) were still making money on the flight because the hold was full of US Mail.
That was a quality experience we'll likely never see again.
(Then again, I also once flew London to NYC one row in front of the smoking section - that's also a quality experience that I won't miss never seeing again)