Has anyone ever purchased a prepaid AMEX card (with cash) and used it to renew their SA membership?  If so, did you register the card first with AMEX?
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I previously renewed my membership using Google Play (learned about it here) but Google no longer supports the SA app.  I'm still searching for a way to effectively renew without a real world cc.  Thanks.

... but I have never used them to pay for SA.  

I think the biggest issue with prepaid cards is not the brand (AMEX, Visa, MC) it's the issuing bank's country.  

SA uses a non-US payment processor.  Gift cards are a HUGE target for money laundering and criminal use. So many US banks will not allow their gift cards to be used in cross-border payments, especially if the payment is NOT for a tangible good, like a toaster or furniture.  The very reason you are using a gift card for a legal activity (paying for a dating site membership) with "untraceable" funds, is the same reason that criminals use gift cards, except the criminals are buying the gift cards with the proceeds of their criminal enterprise.  

 
I don't have a solution to this, other than my suggestion to get a separate bank account and card in your own name at a different bank using an alternate mailing address. That's not anonymous, but it's not likely to be noticed by your SO.  

 
Life is good

 
The Cat