At the top of the country listings and Pick-a-Perk, you will find some panels highlighted in yellow who are advertisers. These advertisers rotate positions, and there is not an order to them. These panels help keep SurveyPolice free; operating a website of this magnitude has sizable costs, so rather than charging users for access to SurveyPolice, we chose to go with having advertisers instead. As spider pointed out, it is similar to Google's model.
Advertisers are not treated differently in terms of reviews, as we are very careful to maintain the integrity of SurveyPolice. Although we mention advertisers in blog posts, etc., whether it's the actual rankings, Pick-a-Perk, the forum, the Survey Tracker tool, and more, you will find them mixed in with content that contains very little advertising (and in some cases no advertising) at all. Again, we don't plaster ads everywhere, mislead our community users into signing up with panels, nor do we charge any fees for accessing (what we feel) is pretty quality information.
Thank you ksedwar! Your appreciation of our work along with the rest of the survey taking community is what keeps us going.