Sketchy like Greyhound? Any company that I have to do a chargeback with permanently gets labeled a sketchy company in my mind. The ones I can remember though are big brand name companies.
I cancelled a subscription to XM and they kept billing me. I called to recancel and get a refund, but neither happened. So I did a chargeback.
That's typical of the experience that would lead me to file a chargeback. If I was billed for a service that I didn't receive and my first attempt to go through customer service fails then I immediately ask my credit card for a chargeback.