This represents a significant drop in price for the 1st generation MacBook Air. The 1.6GHz model originally retailed for $1799 but has since been replaced by the NVIDIA-based MacBook Air that was introduced in October. Specs for the new machine are roughly similar, though, the graphics card has been upgraded to a faster NVIDIA integrated chipset.
The offer runs until the end of the month (or presumably when stock runs out).
MacRumors financially benefits from these sales, but this was also felt to be of genuine interest.