There are already a couple of ways to help prevent charge abuse by merchants.

Several card issuers already support either single-use numbers, where you get a number issued that works exactly one time for a maximum amount you specify, or enhanced authorization, where you have to verify through the issuers website every time an online charge is processed.

Oddly, almost no-one I've talked to is aware of the programs that already exist (and often for free) to help with fraud.