[londons_explore]

In many of these cases, the "A/B test" may have been accidental.

Running a software rollout is frequently done slowly, datacenter by datacenter, and during that time some people might see one version and others might see another.

From the users perspective it looks the same as an A/B test, but the difference is nobody was looking at the results...

[SahAssar]

Almost any user-noticable change (that is not a bugfix) is run as a AB-test for a few weeks in my team to verify that it does have the intended impact. I'd be surprised if there aren't teams at google, amazon, netflix and similar organizations that work similarly.