Devin Coldewey :

It’s no secret that ad blockers are putting a dent in advertising-based business models on the web. This has produced a range of reactions, from relatively polite whitelisting asks (TechCrunch does this) to dynamic redeployment of ads to avoid blocking. A new study finds that nearly a third of the top 10,000 sites on the web are taking ad blocking countermeasures, many silent and highly sophisticated.
 Seeing the uptick in anti-ad-blocking tech, University of Iowa and UC Riverside researchers decided to perform a closer scrutiny (PDF) of major sites than had previously been done. Earlier estimates, based largely on visible or obvious anti-ad-blocking means such as pop-ups or broken content, suggested that somewhere between 1 and 5 percent of popular sites were doing this — but the real number seems to be an order of magnitude higher.
 The researchers visited thousands of sites multiple times, with and without ad-blocking software added to the browser. By comparing the final rendered code of the page for blocking browsers versus non-blocking browsers, they could see when pages changed content or noted the presence of a blocker, even if they didn’t notify the user.