You should check to see if the more or less World Wide moratorium on sales tax for the net can apply to you. The US government has that set up... currently talking about extending that time period. I think its for the very reason you are talking about. It would break the bank for webmasters to gain the technology to figure out where everyone is!
I'd think an attorney would be the one to ask about his sort of thing, not the accountant. We have both and our accountant asks us to ask the attorney in some cases and then she goes from what the attorney says. The web is still new enough that accountants can't work with clear cut tax laws and they usually will err in the favor of taxes, if they aren't positive.
