a friend from college got suckered, er, persuaded to sell Cutco one summer. I don't think she even sold one knife the whole summer. On the bright side, 10+ years later, the knives from her demonstration set are still going strong!
I have some of the Gensu knives. i dont know about cutting though a coke can, but they work well for me. I have had them for about 8 years.
I have Ginsu as well. They stay relatively sharp, but not as sharp as they were as new. The other infomercial you might be thinking of is Miracle Blade.
Yep, it's Cutco i believe. They recruit people to be their salespeople too, i know of a few people who started doing that after high school.