That being said, Google is fine with it as long as you do it properly (you can't have two different AdSense IDs on the same page
What you said there above, I was about to say
that's not a problem seeing as only one advert gets displayed in the first posts of every page of a thread. Then I just realised I'm showing one advert in the header area that gets displayed also (making two). The single sidebar advert doesn't get displayed in threads, so that's not an issue. Does that mean the banner in the right header area (
that does use my adsense banner code only), would it conflict with the one shown in the first posts of threads using members AdSense code at times. Two different banner ID's used on one page like you say.
That being said... we removed it a few years ago because it was just more hassle than it was worth. You tend to attract spammers or people who think they are going to get rich by posting worthless/mindless crap on your site.
I know exactly what you mean by that, but some forums are excluded from showing adverts in first posts using conditionals, such as "private hidden and paid subscribers" forums. Any spam threads could be moved to a forum that in effect removes their banner with it at the same time. Such as a spam bin forum that adverts have been excluded from showing up in. Simple one click (move thread) to remove it.
This is the new full conditional I use now, that makes sure the advert gets dislpayed on all other pages in a thread in the first posts, along with excluding members from seeing ads and letting you choose which forums can be excluded.
Code:
<xen:if is="{$post.position} % {$xenOptions.messagesPerPage} == 0 AND {$message.customFields.adsenseclient} AND {$message.customFields.adsenseslot} AND !in_array({$forum.node_id}, array(99,126,129)) AND !{$visitor.user_id}">
It's in plain sight, it says "68% publisher revenue share" in Adsense. I got scared because the number would mean that the other companies gets all of your advertising dollars.
It's not a revenue sharing scheme were you get 32%, the member 68%. They use their own banner PUB and SLOT number taken from a 728x90 banner advert they must create in their own AdSense account first grabbing the numbers from it. They make all money earned from their banner clicks and actually show their own banner.
There's a big difference in that respect compared to the old idea of splitting the money made with the site owner based on percentages. This thread on my forum best explains it.
Link:
http://mrgtb.com/threads/adsense-revenue-earning-scheme.971/#post-1248
The way I look at it, is like this. Your offering people an incentive to post, they can make money from it rather than making nothing from their posts. You can argue your making nothing from their adverts shown using this method, but if gives posters more of an incentive because of that knowing they keep everything made. Plus, your still showing adverts in other forum areas they make nothing from, along with yours getting displayed in the first posts of threads you make.