The big question! You can have all the personalization scenarios in the world, at some point you want to know what the hard numbers are. Sitecore gives the opportunity to test components, however A/B testing our personalizations comes with a big issue. Imagine a certain amount of people get to see the non personalized variation (A) while the another number of people see the personalized variation (B). From the second group (B), there are still a number of people who don't get the personalizated version of the component because the rules are not met.
Therefore the question is how can we measure non personalized versus actual personalized content (so the group of people that apply to the personalization rules)? Are there different ways of measuring results in sitecore?