It's the circle of life, I'd always figured: You buy a carpet, you stain a carpet, you use bottle cleaners to smear a carpet, you replace a carpet. Thus, I didn't give Dirt Devil's Spot Scrubber ($50) a second look when it came out last year. But over the past few months, it's removed wine, coffee, and tomato sauce from my carpet like magic. What's the secret? I asked Dirt Devil's Rob Matousek.