You might remember my other takes on PPP: paying for blog posts isn't word of mouth marketing and they're unethical. But I digress...
The explanation from a PayPerPost censor, errr "reviewer", cited their terms of service:
A sponsored post is any post for which you received something (cash, goods or services) in exchange for writing the post.
To clarify, we don't send out products in exchange for a review. Bloggers are asked if they're interested, we deliver the product if so and if they choose to write then so be it. There are never strings attached, unlike what PPP does.
There's also another thread here where bloggers are complaining about "reviewers" from PayPerPost censoring posts for similar reasons. As someone who wrote the WOMMA Blogger Relations Ethics Code, I have to say that I am completely dumbfounded with PayPerPost censoring bloggers.
The real kicker is that PPP says that, instead of disclosing if they've received a product, PPP bloggers should purposely not tell readers that they received a product for free from a firm. So, essentially, bloggers should flat out lie about disclosure in order to help the paid postings "blend in".
In the era of transparency, authenticity and credibility, PayPerPost is clearly not interested in participating in the aforementioned values but instead asking bloggers to destroy their credibility through nondisclosure and controlling their content.