The harm is that it hurts the market, because it makes competition between email providers on purely the merit of email providing virtually dead. (I'm not sayi

The harm is that it hurts the market, because it makes competition between email providers on purely the merit of email providing virtually dead. (I'm not saying this harm is not "worth it" in some sense, but it's a very real consequence of these giant cross-financed markets - see also mobile operating systems and web browsers.)