Advertising certainly has plenty of negative externalities, but the positive externalities of the free ad-funded services I mentioned are absolutely mind-boggling. Try to imagine living without them (if you couldn't afford to pay for them yourself).
For instead of your ISP spending 20% of their resources advertising (because otherwise they'd lose market share to ISPs that are advertising), they could likely offer email hosting and basic web hosting without you paying any more than you do currently. Competition between companies should be directed towards productive ends (improving their product) else it just becomes a giant zero-sum game of resource wastage.