I do see what you are saying, that the mechanism cannot detect motivation.
That's why things like saying "clicking the ads helps the site" is not allowed. This is what advertisers call "incentivizing" clicks.
So to answer your question all I can say is basically what I've been saying all along, helping the site should not be a factor at all when looking at an ad.
But to answer your question more precisely (and more generally) there are three main types of advertising models: CPM, CPC and CPA.
CPM means cost per mill (impressions). This is a model that pays for page displays, but it's a declining format because the CTR (click through ratio) makes a big difference in the advertiser's results.
CPC is cost per click. This means that if the visitors do not click on the ad the advertiser does not pay. This is good for advertisers because they pay for the results, and is the most common type of advertising here.
CPA is cost per aquisition. This usually means the advertiser pays based on the ultimate result: a sale. Amazon affiliates are an example of this model. In this case impressions and clicks mean nothing and payment is made based on sale or specific lead.
Here on A2K we use all three formats. But it's important to remember that advertisers do not pay to support A2K and A2K is not helped in any way by incentivized clicks because that hurts the advertiser's ROI and subsequently hurts A2K.
What really works is contextual ads, as this generates real interest through contextual relevance.
The text ads we tested were very successful because over 80% of the users here have complete and total "banner blindness". This means that even if the ads interested them they'd not notice because they subsconciously ignore them.
The flip side is that it seems that ignorance is bliss when it comes to ads and people want to be able to ignore them more easily.
Anywho, I'm workin' on alternatives and have approached a big contextual advertiser.