This post was initially titled "Top 6 Varnish mistakes", to echo Espen's blog. Even though his material is three years old, the content is still relevant. Plus, there's a healthy colleague competition going on here, and I can't just mimic Espen if I hope to beat him, so I had to do something different.
Instead, I'm going to compete on brutality: this post isn't about explaining the most common mistakes, but rather the ones that can really kill your service, one way or another. I know it sounds a bit scary, and it is, but that's for your own good, really. So buckle up, and let's see what I have in my Little Shop of Errors.