This case study will be most relevant to those doing media buys. You've probably guessed it, I'm gonna talk about email. You may think you're cool with your fancy traffic sources and advanced tracking platforms, but know this: Email isn't going away. Email is the cockroach of the internet.
Traffic from my email newsletter to my site:

Traffic from facebook to my site:

Notice how the ad CTR is significantly higher. Everything else is equal. Same content, all desktop traffic. I made sure there were no variables other than traffic source. The results are over several months so it's statistically significant.
Social media is notoriously bad for ads and conversions, and this proves it once again. People were simply unfamiliar with my site and/or were eager to return to their newsfeed. My trusty subscribers on the other hand engage with all content, including ads, because they know, trust, and (I hope) love my site. What you see above is just the ad CTR. I am sure that my email subscribers convert for advertisers at a much higher rate than random visitors from Facebook, etc.
So when doing a media buy, I would put sites with strong email lists at the top of my list. All traffic is not created equal as you know. It seems from my experience that people who are familiar with a website will tend to trust it more, which will result in better CTR and more conversions for your ads.
Choosing the right place to run your ads can make a difference that is several degrees of magnitude greater than optimizing your ads or landers. Not that you shouldn't do those things, but you get the point.
One more thing: Conversions from newsletter ads are also extremely high, example:

that's a small example, but if you're selling a $100 or $200 product, it can quickly add up.
I hope this helps you in your media buying endeavors.
OK, that's it. I'm going back to list-building for my next affiliate project. You have well and truly convinced me that it's the way to go!
Shit, this is powerful, I managed to make lists in Poland, from adult traffic for 200-5k emails daily, but there is no platform to send adult emails.
I was sending out male enhancement emails with aweber. You just need to word the emails carefully to avoid getting a high spam rating.
They won't let you send any porn related emails but certain adult niches are ok.
^^Yep, I've confirmed with aWeber reps in the past that they don't mind adult niches - they just don't like porn.
Wow, this is great! Thanks, Ill sign up with aWeber ASAP 
Those are some impressive conversion rate numbers!
mcr and cmdeal are always on some next level ish that gets 'dem gears movin'
Rad post man!