As someone who's done this (not for ashleymadison), it's not necessarily 'easy'. Also, many sites that take recurring payments won't allow you to use a prepaid card.
I've done it for some other sites, though not recurring though. My guess is if there's enough balance on the prepaid card (for a pre-auth?), it will work.
I never used AM, but I assume they authorized payments on a subscription (recurring) basis, like every other dating site. If that's the case, the kind of pre-auth is different, and one which prepaid cards would reject.
