I would like to suggest that you allow advertisers to put in a backup credit card in case there is a problem with the primary card. I've had 2 cases recently where my credit card was declined and all campaigns stopped. If this happens when I'm away on a trip, it's not good to have all campaigns stop for a period of time until I get back to a computer.
Allow for more than one credit card as an emergency backup (this will allow customers not to go offline).
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