Does this seem logical to you?

http://www.adsflip.com/about/

Here's how AdsFlip works.

Simply take a moment to register for a free AdsFlip account, once registered and logged into your account, you then setup the AdsFlip Banner on your website. This banner will allow users on our network to advertise on your website, once a user on your webpage views or clicks on the AdsFlip banner your account will be automatically credited. These credits can be used to advertise your banner on other websites on our network. You then simply upload your website banner onto the network and finally start advertising.

Its simple; receive credit when a user views or clicks on the AdsFlip Banner, then advertise using with these credits.
Seems like publishers advertise for money, not to buy more ads. I'm surprised if they have many advertisers to begin with.