[jdangu]

> For one, there can’t be 2 [clientID, userID] couples with the same userID: with the way mixpanel does things, this is essentially a technically impossible scenario (...) And yet one user can access your site through different clients, leading to a systematic overestimation of the number of visitors hitting your site.

Really? Anyone can confirm this behavior? I'm pretty sure KissMetrics doesn't have this limitation.

[losvedir]

Indeed, and this is why we ended up choosing KM over MP. With KM you just "identify" a visitor whenever you want and if there's already another anonymous cookie, it'll tie together all events retroactively. We couldn't find an easy way to do this with MP when we looked at it.

[duwip]

Yep, it would seem that KISSMetrics has a better implementation where aliasing can be called several times (as stated here: http://support.kissmetrics.com/apis/common-methods.html).

The fact that it links accounts retro-actively though can be dangerous, in the scenario of publicly-accessed devices. I'll have to admit though, this is not the common case.

I guess my personal gripe with what MP and KM are doing boils down to: if you can't infer stuff about who is visiting my website, be honest about it and don't.