Omniture implementation: Fallback visitor ID vs first party cookies

Question

Beginning with code version H.25.3, Omniture introduced a new cookie that will serve as a fallback method in case your third-party cookies are not accepted.

Can anyone tell me if there are any drawbacks when using this method? Why would someone use the first party cookie implementation instead?

Answer 1

I think that the following information answers my question. They come straight from Adobe 1.

Visitor accuracy matches true first party cookies: This solution sets a first party cookie and its rejection rate is as low as any first party cookie implementation.

Visitor Uniqueness: The methodology used to generate the s_fid value does not guarantee a unique value for each visitor. Factors that impact uniqueness include the volume of s_fid values set across the site and the number of concurrent hits from visitors who arrive at the same millisecond. It’s important to note that the odds of this are very low, and you shouldn’t notice an even remotely significant difference between visitor counts using this methodology and using CNAME first-party cookies.

Decrease in visitors after code update: If you update your analytics code to H.25.3 or higher, you may see an overall decrease in your visitor count because of the decrease in overall cookie rejection.

http://blogs.adobe.com/digitalmarketing/analytics/want-a-cookie/

Answer 2

This document has a little additional information on the fallback method: http://microsite.omniture.com/t2/help/en_US/sc/implement/index.html#Identifying_Unique_Visitors

There actually aren't too many drawbacks using the fallback method, however if you're using SSL or defining your own visitorIDs, it will be more accurate.

Answer 3

A s.VisitorID can be used for cross-device stitching i.e. identifying a visitor across different devices since it is set by us by configuring visitorAPI.js.

Answer 4

The main drawback is that IP addresses and other user agent string can very easily be spoofed. While most people don't go out of their way to do this, many browser addons and other software meant to protect the privacy of people will mask or spoof this stuff, and many times it's a default settings. So as privacy concerns grow, more people will look into getting software to protect their privacy, and it will reduce the accuracy of this method.