SpiderJon - 1 hour ago »
If you're watching one channel, but keeping an eye on another, for whatever reason -- eg, a sporting event* you're quite interested in following, but don't want to actually watch all the time.
* football match, marathon, tennis match, or a flat stage in the Tour de France.
Yup I use the Back button functionality on the HDR-FOX T2 in similar circumstances so I am with you that it is useful some times.