It's a last measure for Google since otherwise the percent of people using ad blockers (that block all ads) will become so large that Google will crippled beyond recovery.<p>There hope is that if a blocker is built in natively, new users won't install a third party blocker. And there blocker will allow most all their ads, but block all competitor ad's that are especially annoying. And people will presumably hate ads less.<p>This will most likely backfire since everyone who never considered installing an ad blocker will now have it by default.<p>Then eventually, Google will without question eventually block third party blockers. They will say they unsafe, negatively affect performance, or insert any excuse. Then everyone will be stuck viewing all their google ads.<p>If Google were to block blockers now, they would be destroyed by the public, but assume that if they offer a blocker that there maybe less backlash and hoping people won't leave for Safari or Firefox.