This works, but you better have a sizable and stable business that already has been proven, and now want to increase volume by removing risk and uncertainty from the minds of potential customers.
If you're in the red, strapped for cash and still figuring out if your business works, that would be a hell of a gamble.
Actually it works far better for new businesses. People don't know your product and won't risk it, especially buying online. The guarantee leads to a hell lot of sales and marketing.
People avoid manipulating the little guy and usually the people at your doorstep early on are quite desperate for a solution.
If anything, this scales poorly to large companies, because they get on exploit forums and it's difficult to train staff to make the call differentiating between valid and fake claims.
If you're in the red, strapped for cash and still figuring out if your business works, that would be a hell of a gamble.