[jamiequint]

This article is really making a big deal out of nothing. All the "major issues" brought up here only create problems in edge cases. When you're trying to drive growth or understand your users (the purpose of metrics at the end of the day) you should not be focused on edge cases.

In most cases the reason you care about tracking logged-out -> logged-in behavior is to measure onboarding behavior, understanding what the user does pre-signup so you can do a better job of driving signups. Signup is not a multi-client process in the common case so being able to track multi-client behavior pre-signup doesn't really matter at all.

[duwip]

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.