Apple's fifth-gen iPod touch is unable to automatically adjust brightness of the display depending on your environment because engineers unexplicitly dropped the ambient light sensor from the device. This eyebrow-raising omission is that more puzzling knowing all prior iPod touch versions had that sensor, a common feature on iPhones and iPads as well.
News of this 'discovery' propagated throughout the Interwebs today, but our own Jeff Benjamin made a mention of the lack of ambient light sensor in his video review of the new iPod touch from three days ago...