Sounds good in theory, but as we all know, real world usage can be an entirely different matter altogether. The UV exposure time would be very short indeed once this unit is in the hands of the average user, simply because many people vacuum way too quickly and are easily satisfied once the surface of the carpet *looks* clean. They'd be far better off doing without the UV feature altogether, and taking the time to do a really thorough vacuuming job instead. By that, I mean using several slow, overlapping strokes to remove ingrained dirt and allergens from deep within the carpet, not a quick once-over.
The idea of killing germs in the carpet will no doubt appeal to germophobes, but I shall just stick to daily vacuuming and deep cleaning two or three times a year. IMHO, a sufficiently hygienic environment comes automatically when you maintain a good level of general cleanliness - no magic light needed!