My wire-closet is located close to my bedrooms and noise from the fan is not desirable.

But the main reason for this feature is that system with fans will require constant maintenance.

The TS-109Pro features fan-less design. Cool! Actually It is hot, because the aluminum case is radiator for the HDD and the system board. It feels hot but the HDD runs cooler then other NAS devices I have seen. For more information read this: http://www.qnap.com/images/products/NAS/TS109Pro/Thermal_TS-109_Series_ENG.pdf