In the U.S., many of them are mining and selling our data. Getting off of their DNS service is one step in mitigating this. Also, as others mention, they can

In the U.S., many of them are mining and selling our data. Getting off of their DNS service is one step in mitigating this. Also, as others mention, they can and do monkey with the results. In other words, here, your ISP is in part a hostile entity. At least, in my perception -- and I'm not alone. P.S. Of course, there's the argument against giving Google all your DNS usage, as well... I use a different DNS service from a company with a good reputation that says it's not collecting usage data. Even then, and with the state of our State, who knows...