I would generally agree here, except Crucial seemed fit to issue a warning and say that warranties wouldn’t be honored in the case of a melted adapter. Does make me wonder what their support staff saw that made the company deem it worthy of the effort to write up a support article on it. That said, a good adapter shouldn’t be able to arc which would be the main risk. I tend to make sure my adapters/cables come from known sources to try to minimize the risks that can crop up from cut corners (StarTech, MonoPrice, etc).
Molex to SATA adapter cables are a very simple and cost-effective alternative to buying a new power supply.
www.crucial.com