HOSTS File - Ad.Doubleclick Question

Ad.Doubleclick.net is THE poster boy for the Hosts File site expalining why certain IP Addresses should be blocked. Yet FoxNews.com and some other sites use Ad.Doubleclick.net in their Server routing (witnessed in System Tray -sites May Open BUT target Video doesn't Play ) . I'm not deathly afraid of just Tracking Issues but why would FoxNews.com use it IF it may (ie) open other harmful connections on my computer as stated as possible by the Hosts site? Do all of you Block Ad.Doubleclick.net?? Thanks!