You assume that all transactions can be matched with ZIP codes. Here in.ie ZIP codes mostly do not apply.
Dublin has single or double char postal areas. Outside the city there is no concept of a postcode.
I dare say there are a large number of other places that have credit card holders but no ZIP codes.
During the last general election here in.ie, electronic voting was used in three constituencies as a part of a trial. I believe for the upcoming referendum, this will be expanded to several more constituencies.
Ireland has a reasonably complex voting system. Each voter has a single vote, but can vote for several candidates in their order of preference. (Each constituency has between three and five seats). Even given that complexity, the system seemed to work well. There was about the expected turnout in each count center, and there were few concerns expressed about the usability of the system.
Slashdot Mirror
Dublin has single or double char postal areas. Outside the city there is no concept of a postcode.
I dare say there are a large number of other places that have credit card holders but no ZIP codes.
Ireland has a reasonably complex voting system. Each voter has a single vote, but can vote for several candidates in their order of preference. (Each constituency has between three and five seats). Even given that complexity, the system seemed to work well. There was about the expected turnout in each count center, and there were few concerns expressed about the usability of the system.
Some info is at http://www.environ.ie/electronicvote.html.