If you want to make money on display advertising, you will grasp for whatever pennies you can get

Google Adsense is not always the highest-paying option for a given impression

There are entire companies that do nothing but figure out quietly, without the publisher's having to do anything, what will pay most at a given moment

I agree with what you're saying, but want to clarify that you're talking about 'AdSense' (the display advertisements), not 'AdWords' (the search ads).

Oops.

I had already edited my post to change "DoubleClick" to "Google Adwords" and I got the product name wrong!

Google serves ton of malware ads, they seem to consider it the responsibility of the users to report them.