DDOS is now part of the weather of the Internet. Take it into account or suffer the consequences.
When high-profile sites got attacked by Anonymous, the rest of us could laugh and blame those orgs for bringing down the wrath upon themselves.
But the truth is that those were noteworthy exceptions to the norm, which is that DDOS attacks happen frequently and for no discernible reason.
We would laugh today at a major site that allowed itself to be taken down by a SQL injection. Time to start thinking the same way about DDOS.