It takes one wrong word to put your foot in your mouth. We’ve all done it and, in the process, squandered an opportunity to impress someone (or some crowd).
With copy, you have a chance to slip up on every homepage, product page, or ad.
If you ask most marketers, they will tell you that A/B testing and personalization are two completely different things. I respectfully disagree, and I think this disagreement is at the root of how to use them best together.