A lot, actually.
It wasn't until I started to question the rules, as opposed to taking them for face value, that I began to actually understand the "WHY's" behind this way of eating.
It's also when I realized the importance of a personalized approach to Paleo. If no two people are alike, why should my plate have to mimic somebody else's?
So I eat dairy. I eat white rice. I eat white potatoes. I sometimes drink alcohol. On occasion I have homemade junk food, too.
All these examples have their own justified reasons, for me and my body.
You must learn to ask the WHY's instead of dismissing someone's view point as incorrect simply because it's not what you were told by your friend who works with someone who's cousin's brother eats this way.
Read the books. Entirely. Then follow some blogs and articles, because things are constantly evolving. Some of the first books I read were not in favor of certain foods, such as dairy-- but things change and new information develops and presents itself every single day.
It's important to embrace this constant in learning otherwise we will end up spending decades believing false information because no one was up for (respectfully) questioning the experts.
So next time you see dairy, grains, potatoes, legumes or even vegetarian options on someone's social media feed, consider the fact that they may just be a pro, who's learned how to properly break the rules.