Since the number is locked to a particular vendor, that number cannot be used elsewhere which is great protection if that vendor's database is hacked.
Also, since you can set a limit and expiration date you automatically win the argument with companies that refuse to stop charging your card.
Oh, and you can manually cancel that number at any time.
Re: Shopsafe
Yes, I use that all the time with on-line orders now.
But back when I had the problem with the ISP, I was using my Amex card. Happily, I just refused the charges, and let Amex handle it. The problem went away very quickly, and I didn’t get hit for the additional charges.
Mark