If I'm looking to buy something and don't know where to buy it, the first thing I do is a Google search followed by opening all the ads above and beside the results in tabs.

I've also been captured by retargeting campaigns by web services. Quite a few YC-funded companies run them. You only see their ads after you've been to their site... but they follow you all around the web, everywhere AdSense/DoubleClick reaches, which is 90% of all display advertising.

On banner ads? Lower-income middle-aged people outside large urban areas with a propensity to visit auction and gambling sites.

That's not the point, though. Being exposed to a brand's banner ads increases one's likelihood of searching for the brand, visiting the brand's website, making a purchase online, and making a purchase in a store.

There's a reason why online advertising technology today is so focused on measuring 'view-through' conversions - as the pool of heavy clickers decreases, click-through rates are less and less correlated with the actual effectiveness of the advertising.

For a while I was clicking on adds that I disliked to cost the people making them money and gives it to the site I like enough to be on. But, I think that just promotes people making more adds like that.