Agreed, these are edge cases. They did create a lot of questions for me though, and made the whole thing rather confusing as a user. As to how much of an issue

Agreed, these are edge cases. They did create a lot of questions for me though, and made the whole thing rather confusing as a user. As to how much of an issue these edge cases represent, I find it hard to get a real sense of it. I guess it really depends on the situation, what you want to measure and the user experience you offer to your visitors.