I'm not sure I'd call it a scam, but I would say "High risk". If you look at the Terms of Service (TOS) :
WARRANTIES, LIABILITIES AND DISCLAIMERS
*
www.instantvirtualcreditcards.com is not held responsible for any prepaid virtual cards that have been compromised or stolen. Any losses or damages will not be the liability of
www.instantvirtualcreditcards.com*
any fraud, deception or misrepresentations by the User, merchant or some unknown entity or person.*
any errors or omissions in the website content.
* the misuse of the web site content or the inability of any person to use the site.
www.instantvirtualcreditcards.com service is limited to providing the User with a payment facility and
does not guarantee the quality, safety or legality of the transaction the User is undertaking. www.instantvirtualcreditcards.com will not be liable for any goods or services for which the User pays using this service and will not be liable for any charges, taxes or other duties in relation to such goods or services.
and from their own FAQ's : - My virtual visa card got declined so I would like to get a refund. Is it possible?
- Absolutely! We'll refund
95% of the amount on your virtual visa card within a week of your purchase if for some reason your transaction gets declined. We will also refund you if you didn't use the card and no longer need it.
It sounds to me like the only thing they guarantee is that they will take your money. They offer no guarantees for anything else like regular credit card companies do..
I wouldn't call it a scam,
because they tell you upfront they are only willing to take your money, with no other guarantees. But in my book, that does not make them a good choice for a prepaid card. There are plenty of real card issuers out there that do have guarantees on their cards / purchases.