I had a friend attempt to sell for Kirby years ago but they didn't pursue it because it was a door-to-door sales job which they decided they didn't like. The hours were long and sales were hard to get because the vacuum was expensive, heavy and tedious to operate.
I've heard lots of things about the sales people being pushy and their selling techniques questionable which is obviously a flaw,and there are also a few sales representatives that don't treat their staff well. As well selling (and cold calling at that) isn't everyone’s cup of tea.
Maybe it doesn't represent a great opportunity for everyone but I don't think it's a scam.
If you're applying for a position, it's common sense that you enquire about whether the job is commission based or what the terms of employment are from the onset (preferably in writing) to ensure that the position is to your liking and satisfactory to your circumstances.