This is something many large companies do, because they are unable to fully test everything in an isolated environment. So they test in production with A->B tests or canary tests at THE MOST. It is an extremely common practice at every engineering company that is not dealing with stuff like sending people into space and life or death. The reason why, is if you let it hold you back from releasing, your development slows to a snails pace and you loose to your competitors and never ship. Source: much devops pager duty.