Sponsored posts may not appear consecutively on your Blog. Each Sponsored post must be separated by at least one non-sponsored, original content, post. 'Sponsored' posts apply to both PayPerPost Direct and Marketplace Opportunities, as well as other sponsored posts from competitive services.
So, even if SponsoredReviews, ReviewMe, Loudlaunch, Smorty plus others does not requires non paid interim post, PPP has help them and help us with the above clause so that your blog won't be congested with paid post only.
This give you more change to receive more opp from advertiser because they do not like to advertise in blogs that are full of paid post.
So now, say a big "Thank You" to PayPerPost and then start cracking your head for non paid post, if possible try not to put any link in them, scared they will think that it is paid post too. Like what I am doing here, no link to the blog advertising companies that is listed here because this is a non paid pot. :)