Thanks for this very interesting "walk-through" of what it's like in Oregon...
It's pretty clear to me why they only accept cash, although my conclusions on that are based on "bits and pieces" of direct information that I've received.
Although Mary Jane may be perfectly legal in Oregon and several other locales, that doesn't mean that it isn't still the target of massive persecution by the "powers that be."
I personally know of one company whose ability to accept credit cards was been pulled out from under them by more than one financial organization. They attribute it to the fact that they carry and promote completely legal extracts of the plant - i.e. cannabis oil.
Furthermore, when I recently applied for a business account at Comerica Bank, I was grilled in excruciating detail to verify that the business had no connection with weed.
We live in interesting times.