Well, well. The rise of ad-blocking is beginning to bite.

On Friday, dozens of people took to web forums and social media to complain that they were blocked from their Yahoo email accounts unless they switched off their ad blockers.

The issue seems to have first appeared early on Thursday when “portnoyd,” a user on the AdBlock Plus online support forum, was served a pop-up with an ultimatum: Turn off your ad blocker, or forget about getting to your email.

Yahoo confirmed the reports, which were discovered by Digiday. Yahoo, based in Sunnyvale, Calif., did not say how many users were affected.

“At Yahoo, we are continually developing and testing new product experiences,” Anne Yeh, a Yahoo spokeswoman, said in a statement. “This is a test we’re running for a small number of Yahoo Mail users in the U.S.”

Don’t you just love that guff about “developing and testing new product experiences”!

In the end, the targeted-ad-based business model is not sustainable. Wonder what will replace it.