The quick answer is we really can't block YouTube ads, because of how they're served. For the longer answer, read on. The way we and most other services block ads is by filtering out domains that serve them up. For example, when you visit a particular well known Android blog—who shall remain nameless because this isn't about calling them out—your browser will make a whole bunch of requests. Those that are for the site's domain and for the domains of resources like fonts and graphics are handled normally. But the requests for domains that serve ads and tracking scripts are blocked. For this site the blocked requests include: pagead2.googlesyndication.com, ads.pro-market.net, sb.scorecardresearch.com and www.google-analytics.com, just to name a few. The thing with YouTube is the ads shown in videos are served from the same domains that serve up the videos themselves. So in other words, if we block the ads then we end up blocking the videos too.