You can use 1 credit card to open several accounts but: if you are planning to promote the same business (same keywords/same business) -and/or- use voucher codes for these accounts This is against TOS and probably they will get you soon. People has been permanently banned trying this before.
well, I do not do this but if your are completely intent on using multiple voucher codes you could go through the trouble of opening several Visa Gift Cards with preloaded amounts of money to get your advertising started. Those cards are not attached to any name/address information. They simply are "Visa Gift Cards." You could then use a different name and individual gift card to setup accounts and use vouchers. Eventually those cards would run out of money though, then you'd have to use your real card. That might be when they catch you though. Dunno, I never tried it, but I assume that would work. I'm not going to be the test subject though have fun with that lol
basically it has to be allowed, coz there are many companies who dnt like to use their credit card and they give their campaigns to be managed by adwords professionals, and its certain that there has to be a seperate account maintained per company setting multiple accounts with a credit card for coupon purpose mite not be allowed, may be 1-2 should be ok not more then that per card. im using myself 2 coupons for my customers, though i have stoped it there , as i cant give offers to all customers for adwords coupons pack.