Often, Internet service or telecom providers, or providers of DDoS mitigation services are able to use this headroom and other creative techniques to mitigate DDoS effects.
It has some ideals: Anonymous tends to defend free speech and fight internet censorship, as with the DDoS-ing of the web sites of MasterCard, Visa and PayPal after they nixed funding services to WikiLeaks, and the DDoS-ing of Tunisian government Web sites.