I hope you don't mind me butting in here..
A zero iframe is kind of a misnomer in some ways as it doesn't have to be 0 pixels by 0 pixels to be a bad or cheating iframe. An invisible iframe or an inappropriate iframe is probably a better way to think of it.
An iframe that is 0 x 0 pixels is invisible. But if you make it 100 x 0 it's still going to be invisible. The ones on Bonniemails are in a banner iframe and are 1 pixel by 1 pixel, which is still too small to see what is inside the iframe - that's only the size of a full stop/period on a page, you can't see a full website stuck in an iframe that size! It's also a problem if the iframe is larger, say banner sized and it's loading full sized webpages in there (this would be the inappropriate iframe rather than the invisible iframe).
On bonniemails PTP there is a banner sized iframe
CODE
<iframe width="468" scrolling="no" height="60" frameborder="0" src="http://www.mfhelper.com/ad.php" marginheight="0" marginwidth="0">
And that contains the invisible iframes that are set at 1 pixel by 1 pixel
CODE
<iframe width="1" height="1" src="http://rover.ebay.com/rover/1/710-53481-19255-0/1?type=1&campid=5335951539&toolid=10001&customid=">
</iframe>
<script type="text/javascript" src="stat.js">
</script>
<iframe width="1" height="1" src="http://www.0001onlinegames.com/adincent.php">
</iframe>
<iframe width="1" height="1" src="http://www.0001onlinegames.com/content/adsense/banner.php">
The first one is an ebay page. It's cheating to put an ebay page inside an invisible iframe.
I left that loading for some time and after a few minutes something has actually started doing autosearches for me.
The more 0 iframes or invisible or inappropriate iframes there are on a webpage, the harder it is for a PO who is sending the ad to check it for viruses and autosearches.
Additionally the more webpages you stick in iframes on a webpage, the heavier it will be to load up on my PC, so my PC gets locked up constantly from so many webpages trying to load at one time.
Then another problem with 0 iframes is that they can be used to hide viruses.
Also a lot of the inappropriate iframes, mostly coming from the 3rd party networks, loading webpages in banner sized iframes have a tendency to break out of the frames, because the sites they are loading in the frame don't want people cheating to get clicks to their sites that they have to pay for as if they were genuine clicks, so they break frames and then what happens? Does the member promoting the PTP get credit? What about the person who paid for the spot in one of the rotators on the page, once that page breaks, no one will be able to see their website and if you hit the back button you'll be shown a different page in the rotator.
As I've been typing, the bonniemails has had something break the frame on that coincidentally and I'm now viewing a webpage with 4 webpages stuck in iframes.
Anyway the main thing is it's not just 0 x 0 pixel iframes that are the problem. The main thing is does the iframe size fit what is inside it, can you see everything clearly, and is it cheating or is it carrying a virus. Those are the things most of the decent POs (like Ron) are trying to avoid having on their sites or sending in ads on their sites.