I’m guessing Sony and Microsft won’t be calling attention to their inability to invest sufficiently in anti-hack/anti-DDOS precautions in their respective annual reports to investors.
Yep, although its very tough defending against a DDOS attack.
It's theoretically impossible to have an anti-DDoS on an open network: this is because it has to be receptive to new, previously unknown senders/clients.
You could limit things by having a closed network, with an open-network essentially being a gateway to the closed network, but the open portion would still be vulnerable.
In a purely closed network you could achieve anti-DDoS by (1) having all nodes w/ a [known] static address, (2) rejecting all traffic from an unknown address, and (3) when a node starts saturating the network, exclude it for a length of time.