PayPerPost is a terrible site that pays bloggers a fixed fee to write about certain topics or products. Where PayPerPost doesn't require disclosure of this information, newcomer ReviewMe does :

People ignore ads. In much the same way that banner blindness set in, many publishers have noticed their contextual ad click through rates and earnings drop over time.

Because our reviews are not formatted to look like ads, publishers are able to deliver more attention and value than through advertising via any other marketing channel.

ReviewMe uses an algorithm based on Alexa, Technorati and other statistics to determine the importance of a blog and payment is based on the importance.

I wonder where all this is going..... According to Techcrunch, pay-to-shill business model is spreading like a virus.