The Google AdSense blog made a post to clear a few minor policy differences surrounding — promotion for referrals & standard AdSense for content ad units.
Recommending products vs. encouraging clicks: You can endorse or recommend products you've chosen to refer on your sites, but it’s advisable that you only make recommendations when you're familiar with the specific product and you've decided not to use the 'Pick best performing ads' feature for that ad unit. For example, if you're familiar with a specific travel agency you're referring, you may use language such as “I use this agency and recommend it to book your next vacation.” By being honest with product recommendations, you can help build user loyalty and trust, which will benefit your site in the long run.
You may be wondering why we allow publishers to call attention to referral units but not standard ad units. This is because there are significant differences between these two types of ads, the most important being that advertisers only pay for traffic from referral units if the user performs a specific action the advertiser has designated (such as making a purchase from the site or signing up for a newsletter). Please keep in mind that there is a fine line between recommending a product and encouraging your users to click on a referral button for personal profit. Publishers may not ask users to click on the referrals to help them earn money, and may not refer themselves to their own referral products. In addition, publishers may not draw unnatural attention to their referral units with arrows pointing to the units or other similar methods.
Using online advertising: As is true for all sites displaying AdSense ad units, referral units, or search boxes, your site must comply with Google's Landing Page Quality Guidelines (LPQ) if you'd like to use online advertising of any kind as a traffic source. The term 'online advertising' refers to a range of methods, from advertising programs such as AdWords to posting your site within a link exchange or in a forum. However, if the primary purpose of your site is to generate conversions from referral ads, you'll need to go one step further before advertising your site. You'll need to first receive permission from the advertisers whose products you're referring before advertising your site or their products. Please note that Google has made the decision to not allow publishers to use online advertising for any of the Google products or those of our Google Pack partners.
Google, AdSense, Referrals, Online Advertising, Online Ads, Policy