I've had RAID appliances and home servers for years that are 'always on'...until the electricity goes out. The UPS gives me about 20 minutes to shut things down nicely.
Unless Western Digital have a UPS monitor for this box, or designed it to prevent data loss (internal battery for the RAM, caps or battery to gracefully shut down the drives), it needs a power switch that can be found and used by someone in underpants stumbling in dim light, and which doesn't require WiFi to operate.
This new My Cloud looks like a step up from their previous offerings. iSyncing aside, I'm impressed.