Both of these articles say the keyboard is back lit. One is from 2007, and one from March of 2011. The keyboard doesn't look back lit and most manufacturers don't miss on including features built into their product.
But who knows?
Pros and Cons of the Microsoft Natural Ergonomic Wireless Backlit Keyboard
Backlit and can be used in the dark or at night.
Designed to fit a typist's hands naturally and comfortably.
Built in zoom feature.
Programmable hotkeys that can be customized for any application.
E-mail and Internet hotkeys that make accessing e-mail and Internet applications simple.
Works up to thirty feet away from the receiver.
Does not possess a PS2 receiver.
Quite large in size.