So I work at DeviantArt, and we actually saw this in real-time. A few years ago, we added external ads all over the place, and had to add a whole framework to detect “ad-unsafe” works that wouldn’t get ads served against them. So we only got ads against a percentage of views, and people were getting pissed at the ads and leaving.

So we tore the ads back out, traffic’s recovered, and a focus on providing actual tools for artists to make money through the site has meant we’re doing better without ads than we were with ads.